蹺蹺板怪物

by Kōtarō Isaka, 伊坂幸太郎, 王華懋 (Translator)

1988年，美日貿易衝突登上新聞，鬧得沸沸揚揚，然而，北山宮子和婆婆之間的問題，甚至沒有成為街坊飯後茶餘的話題。

身為前特殊部隊的間諜，宮子自認是溝通專家，面對婆婆卻總是失控。一天，陌生的保險推銷員上門，觸發了她對婆婆的疑心──為何婆婆的親人都死於非命？

另一方面，在製藥公司上班的丈夫直人，不慎發現大客戶在進行醫療詐欺，一向照顧他的前輩也牽涉其中。內憂外患夾擊，夫妻倆的生活掀起了萬丈波瀾……

／／

2050年，AI系統掌控一切。重要的事最好不要透過數位裝置或網路進行，祕密交談的內容必須透過紙筆書信傳達，成為年輕世代的共識。

水戶直正，非效力於公家機關的獨立信差。此刻，他坐在新幹線列車裡，一名男子忽然在身旁坐下，委託他送信給老友。不料，那竟是一封遺書──男子隨即跳車自盡。千辛萬苦達成使命，對方卻不容分說地帶著他逃亡。原來委託人是AI系統的開發者，要求老友摧毀系統。於是，兩人成為國家通緝的對象。更不妙的是，水戶自小的宿敵──刑警檜山，在背後窮追不捨。

循著信中的線索，他們找到一位退休的繪本作家，在曾是間諜的她大力協助下，冒險前往最終目的地。只是亡命途中，水戶模糊的童年記憶愈來愈清晰，而且居然與眼前經歷的一切有密切的關係……

「無時無刻都在發生衝突，這就是歷史的循環吧。」
「你是說，和平是建立在別人的犧牲之上嗎？」

Genres: Science Fiction, Mystery, Fiction, Thriller, Japan, Fantasy, Mystery Thriller

400 pages, Paperback

First published January 1, 2019

About the author

Kōtarō Isaka (伊坂幸太郎, Isaka Koutarou) is a Japanese author of mystery fiction.

Isaka was born in Matsudo City, Chiba Prefecture, Japan. After graduating from the law faculty of Tohoku University, he worked as a system engineer. Isaka quit his company job and focused on writing after hearing Kazuyoshi Saito's 1997 song "Kōfuku na Chōshoku Taikutsu na Yūshoku", and the two have collaborated several times. In 2000, Isaka won the Shincho Mystery Club Prize for his debut novel Ōdyubon no Inori, after which he became a full-time writer.
In 2002, Isaka's novel Lush Life gained much critical acclaim, but it was his Naoki Prize-nominated work Jūryoku Piero (2003) that brought him popular success. His following work Ahiru to Kamo no Koin Rokkā won the 25th Yoshikawa Eiji Prize for New Writers.
Jūryoku Piero (2003), Children (2004), Grasshopper (2004), Shinigami no Seido (2005) and Sabaku (2006) were all nominated for the Naoki Prize.
Isaka was the only author in Japan to be nominated for the Hon'ya Taishō in each of the award's first four years, finally winning in 2008 with Golden Slumber. The same work also won the 21st Yamamoto Shūgorō Prize.

Reviews

[Makmild · Rating 3 out of 5]

เรื่องสั้นสองเรื่องที่ว่าจะต่อกันก็ไม่ได้ แต่มีเซตติ้งโลกเป็นโลกเดียวกัน ยังคงความเบียวแบบอิซากะไว้เต็มเปี่ยม ความบังเอิญแบบที่ได้ตะโกนอย่างเดียวว่าได้หรอพี่ กับฉากบู๊แม้ไม่อลังแต่ก็ทำให้จิกตีนได้ และตัวละครปั่นๆ ที่ชุงมุกตบมุกกันเองไม่มีช่องให้คนอ่านได้ช่วยเลยแม้แต่น้อย และคงเพราะแบบนี้แหละที่ทำให้เราอ่านจบแบบรวดเดียวแต่ละเรื่องได้เลยเพราะอยากรู้ว่าความไม่ลงรอยของแต่ละเรื่องจะจบลงที่ตรงไหน

ชนภูเขากับชาวทะเล
: มีความเหมือนพ่อบ้านใจกล้านิดหน่อยผสมกับคำอธิษฐานของโอดูบอนอีกนิดหน่อย โดยรวมแล้วสนุกตามมาตราฐานอิซากะ พอเป็นเรื่องสั้นขนาดยาวแล้วมันเลยกระชับๆ มีความบังเอิญแบบอย่างนี้ก็ได้หรอผสมกับคดีที่เกิดขึ้นและฉากบู๊อันน่าระทึกได้อย่างลงตัวเหมือนขนมบานอฟฟี่ การเล่าสลับมุมมองตัวละครสามีผู้อยู่ตรงกลางระหว่างแม่ผัวลูกสะใภ้ก็ทำได้ดี การเล่ามุมมองความเหนื่อยยากจากฝั่งภรรยาก็น่ารัก มีฝั่งแม่ผัวที่น่าสงสัยว่าไปโยงกับจักรวาลอื่นๆ ของอิซากะปะเนี่ย

ปรปักษ์
: เป็นเรื่องที่สองในเล่ม โดยอยู่จักรวาลเดียวกันคือจักรวาลที่มีชนเผ่าทะเลกับภูเขาเป็นปรปักษ์กันอยู่เสมอ แต่เวลาเคลื่อนผ่านไปยังอนาคตที่ไกลกว่าปัจจุบันนิดหน่อยไม่มากนัก และเปลี่ยนตัวนำเป็นเด็กชายผู้รอดชีวิตจากอุบัติเหตุรถยนต์ทั้งคู่ ซึ่งเรื่องนี้งงกว่า ซับซ้อนกว่า เล่นใหญ่กว่า มีประเด็นใหญ่กว่าเรื่องแรก ทั้งด้านตัวตน ทั้งด้านสังคม ส่วนเรื่องความสัมพันธ์ดรอปลง ส่วนตัวเลยชอบเรื่องแรกมากกว่า

[Dan (ThatBookIsOnFiyah) · Rating 5 out of 5]

Overall 4.5/5 stars, rounded up. This story is the first that I have read by Kotaro Isaka, although I have seen the movie based on Bullet Train. I was expecting something different from this author than what I read, but I was very pleasantly surprised. The prose is wonderful. I attribute this to both Isaka’s writing and Sam Malissa’s translation.

Seesaw Monster covers many thematic elements. It delves into personal relationships and the mystical connections among people and events, it has elements of science fiction - an AI potentially gone bad, and includes thriller aspects that keep the action moving along. The story is told in two distinct parts in two different time periods with (mostly) different characters, but keeps the reader entertained and invested throughout both parts. There are hints throughout the story that leads the reader to various possible conclusions before the ultimate ending that is left partially unsolved.

This will certainly not be the last Kotara Isaka book that I read and I highly recommend that everyone read this book. It has something to offer for all readers, but especially those who enjoy a good thriller with personal interactions and character development.

[John · Rating 5 out of 5]

Rounded up from 4 5 stars

[Art Mlang · Rating 4 out of 5]

สนุกดีครับ โดยเฉพาะ เรื่องแรก

[Jake · Rating 4 out of 5]

The first part had me wondering where Isaka was going with this. It was good but seemed sort of rushed. After reading the second part though it all came together. I still feel like both stories could've been elaborated, but thought it was a cool idea to have one complete story lead into another that takes it up a notch.

[Natalie H · Rating 3 out of 5]

September 2025
Hardback edition

I'm gutted I didn't enjoy this one more. Snapped up from Waterstones from the new releases. Interesting book. Two stories. Seesaw monster on one side, on the flip side Spin monster. The story went over my head. Kept pushing the sea and mountain people, the ones that just can't get along. The first duo was painful together, felt sorry for the husband being stuck between his mother and wife. The secret agent thing was interesting and I did like them when they joined together.

The other story is set further on and does have the wife from the first in it. This one was out there with the hidden camera in the eye. Again it pushed the sea and mountain people, but this one felt like forced prophecy. I didn't like the neutral mediator. I'm curious if anything changed when the guy woke up. Took a few stop and starts. Preferred the second story.

[JillV · Rating 4 out of 5]

เรื่องแรกให้ฟีลคล้ายๆ พ่อบ้านใจกล้าสายนักฆ่า แต่เป็นเวอร์ชั่นที่ภรรยาเป็นสายลับ ส่วนสามีไม่รู้อิโหน่อิเหน่ใดๆ เล่าปัญหาระหว่างแม่ผัวลูกสะใภ้แบบสอดแทรกอารมณ์ขันสไตล์คุณอิซากะ, เรื่องที่สองเป็นเรื่องของชายที่ไปทำงานส่งจดหมายแล้วเข้าไปพัวพันกับโครงการปัญญาประดิษฐ์ระดับชาติ ทั้งสองเรื่องมีความสนุกน่าติดตามกันคนละแบบ มีจุดร่วมคือ "ความขัดแย้ง" เหมือนกัน อ่านในปัจฉิมลิขิตเห็นคนเขียนบอกว่าเล่มนี้เป็นหนึ่งในโปรเจกต์ที่มีนักเขียนหลายๆ คน อยากรู้เลยว่าเล่มอื่นๆ เขียนออกมาแบบไหนกันบ้าง

[colorless tazaki · Rating 4 out of 5]

ชนภูเขากับชาวทะเล (4/5) - เรื่องนี้ค่อนข้างชิวเมื่อเทียบกับเรื่องอื่นๆของอาจารย์ ไอเดียไม่ได้แปลกใหม่อะไรมาก แต่ก็มีจุดเซอไพรส์อยู่นิดหน่อย ว่าแต่ว่าอาจารย์ชอบเรื่องแนวนั้นซะจริงนะ 😂😂

[BlurbGoesHere · Rating 5 out of 5]

Kotaro Isaka carefully interlaces long threads of intrigue, adventure, and drama to create a unique pattern of excitement that is nearly impossible to resist. What are the odds that a simple, unsuspecting man would marry a woman whose ancestors had been warring against his mother's? Both women are skilled assassins who simply can't stand each other. Of course, he dismisses their angry comments as commonplace bickering between a wife and mother-in-law. That is, until he is kidnapped and the two women are forced to join forces to rescue him. Meanwhile, in the future, only the written word is safe from scrutiny, as the watchful eyes of technology never tire.

Leaving The Bullet Train behind, Isaka sets his sights on a story that is equal parts comedy, family drama, and science fiction. His signature style shines even brighter while tackling the impossible.

This book is a must for Isaka fans looking for an adventure spanning the ages. I can't recommend it enough!

[GONZA · Rating 3 out of 5]

I have mixed feelings about this book, which started out at a fairly high pace despite the cliché (hatred between mother-in-law and daughter-in-law); the pace, however, then dropped and I struggled to disentangle the various points of view that changed abruptly throughout the story. I have read better things from this author.

Ho dei sentimenti contrastanti riguardo questo libro, che é partito con un ritmo abbastanza alto nonostante il cliché (odio tra suocera e nuora); il ritmo peró poi é sceso ed ho fatto fatica a districarmi tra i vari punti di vista che cambiavano repentinamente nel corso della storia. Ho letto cose migliori da questo autore.

I received from the Publisher a complimentary digital advanced review copy of the book in exchange for a honest review.

[Billy · Rating 4 out of 5]

This is the first book by Kotaro Isaka I've read, but if this book is any indication of the quality of his writing (and translations), it won't be the last. The first half, the title novella of the book, is a story about the rocky relationship between a wife and her mother-in-law that quickly turns into a mystery and thriller, as the wife is a retired spy who finds she must get to the bottom of this conflict. The second half, Spin Monster, is a near-future tech thriller about a courier that gets caught up in a race against an AI that has become malevolent and finds himself repeatedly up against an old classmate he has a history with. Weaving between the two are some characters and a theme of eternal conflict as explained by a fable, the latter of which seems incongruous in Seesaw Monster until it is fully expanded upon in Spin Monster but ultimately comes full-circle in a mostly satisfying way. A very good read, highly recommend.

[Ruirui · Rating 5 out of 5]

มีสองเรื่องในเล่มเดียว 1.ชนภูเขากับชาวทะเล เซ็ตติ้งปลายยุคโชวะ (ยุค 80s) ให้อารมณ์เหมือน Mr. & Mrs. Smith เวอร์ชั่นแม่ผัวลูกสะใภ้ 2.ปรปักษ์ เซ็ตติ้งโลกอนาคตอันใกล้ เรื่องของชายสองคนที่รอดมาจากอุบัติเหตุเดียวกัน ��อบเรื่องที่สองมากกว่าเพราะชอบการดำเนินเรื่องที่ตื่นเต้นกว่า และมีประเด็นเรื่อง AI ที่เข้ากับยุคสมัยนี้มากๆ แต่ประเด็นนึงที่เหมือนกันในทั้งสองเรื่องคือคนเราจะอยู่ร่วมกันในความขัดแย้งยังไง ความขัดแย้งมีเพื่ออะไร ประเด็นนี้ก็ดีเหมือนกัน

[Shaina · Rating 3 out of 5]

Thank you so much to NetGalley and Kotaro Isaka for providing me with a complimentary digital ARC for Seesaw Monster coming out July 15, 2025. The honest opinions expressed in this review are my own.

I really enjoyed other books by this author! I love Japanese novels. I’m not sure about this book. I didn’t like it as much as other books I’ve read by him. It wasn’t like Bullet Train. I think I wanted more mystery and suspense. The first half was better than the second. I would check out other books by this author.

[Simone Beg · Rating 4 out of 5]

3.5

A bit juvenile and not fully hashed out at times. Still an entertaining read

[The Bookish Elf · Rating 4 out of 5]

Kotaro Isaka has built his reputation on a foundation of kinetic action, darkly comic dialogue, and labyrinthine plots that converge with mathematical precision. From the international success of Bullet Train to the philosophical violence of Three Assassins, Isaka's works consistently blend high-octane thrills with deeper meditations on fate, conflict, and human nature. In Seesaw Monster, translated with nuanced precision by Sam Malissa, Isaka attempts his most ambitious narrative structure yet: a dual-timeline exploration that spans decades while examining the eternal nature of human discord.

The result is both his most intellectually challenging work and, paradoxically, one that occasionally struggles under the weight of its own mythological ambitions.

Two Eras, One Ancient War

Seesaw Monster operates across two distinct time periods, connected by the enigmatic concept of an ancestral feud between "Sea People" and "Mountain People." In 1980s Japan, pharmaceutical salesman Naoto finds himself caught between his feuding wife Miyako and mother, whose animosity seems to transcend ordinary family tension. When a mysterious insurance salesman named Ichio Ishiguro introduces the mythology of ancient bloodline conflicts, their domestic warfare takes on cosmic proportions.

Decades later, in a near-future Japan dominated by surveillance technology and facial recognition systems, courier Naomasa Mito navigates a world where paper documents have become the only truly secure medium for sensitive information. When Mito encounters his childhood nemesis Kagetora Hiyama—now a police detective—on a routine delivery, both men are drawn into a conspiracy that echoes the ancient patterns of conflict their predecessors experienced.

Isaka's decision to structure the narrative as parallel stories rather than a straightforward chronological progression demonstrates his continued evolution as a storyteller. The 1980s timeline captures the economic optimism of Japan's bubble era while exploring intimate family dynamics, while the future timeline presents a techno-thriller examining privacy, surveillance, and the persistence of human nature in an increasingly digital world.

The Mythology of Inherited Conflict

At the heart of Seesaw Monster lies Isaka's most philosophically ambitious concept: the idea that some conflicts are not personal but archetypal, passed down through bloodlines like genetic predispositions. The Sea People versus Mountain People mythology functions as both plot device and thematic framework, suggesting that certain antagonisms are as inevitable as gravity.

This concept works most effectively in the 1980s storyline, where Miyako and her mother-in-law's relationship provides concrete emotional grounding for abstract mythological concepts. Their collaboration on the children's book "I Am Mai-Mai"—featuring a snail with the Lance of Longinus—becomes a poignant metaphor for finding creative solutions to seemingly irreconcilable differences. Isaka demonstrates particular skill in depicting how two people can simultaneously despise and depend on each other, creating something beautiful through their very opposition.

The future timeline's exploration of this theme proves more problematic. While Mito and Hiyama's mutual revulsion is viscerally portrayed, their connection feels more manufactured than mythic. The revelation of their shared trauma from a childhood car accident provides psychological justification for their antagonism, but undermines the supposedly supernatural nature of their conflict. Isaka seems uncertain whether he's writing science fiction, mythology, or psychological realism, and the narrative suffers from this indecision.

Technical Mastery Meets Conceptual Ambition

Sam Malissa's translation deserves particular recognition for maintaining Isaka's distinctive voice while navigating complex temporal shifts and mythological concepts. The dialogue crackles with Isaka's characteristic wit, particularly in exchanges between Chusonji and Mito, where philosophical concepts are debated with the casual intensity of discussing baseball statistics. Malissa captures the subtle differences in language between eras without resorting to heavy-handed period markers.

Isaka's world-building in the future timeline demonstrates impressive attention to detail. The society where digital information is inherently insecure, making analog couriers essential, feels both plausible and satirical. The author's background in mystery writing serves him well in constructing the surveillance apparatus that drives the plot, creating genuine tension as Mito attempts to navigate a world where every movement is monitored.

However, the novel's pacing suffers from its structural ambitions. While individual scenes maintain Isaka's trademark momentum, the constant temporal shifts disrupt narrative flow. Readers invest emotionally in one timeline only to be abruptly transported to another, creating a sense of narrative whiplash that undermines both storylines' effectiveness.

Character Development and Emotional Resonance

Isaka's characterization shows notable growth in complexity compared to his earlier works. Miyako emerges as the novel's most fully realized character, a woman whose sharp wit masks profound loneliness and whose creative collaboration with her enemy reveals unexpected depths of empathy. Her evolution from antagonistic daughter-in-law to elderly sage provides the novel's emotional anchor.

Naomasa Mito represents Isaka's attempt to create a more introspective protagonist than his usual action heroes. Mito's car phobia and trauma-induced memory distortions add psychological complexity, but sometimes feel like authorial mechanics rather than organic character development. His relationship with girlfriend Hinata provides necessary emotional grounding, though she occasionally serves more as philosophical mouthpiece than fully realized character.

The supporting cast maintains Isaka's talent for creating memorable eccentrics. Atsushi Chusonji, the tech-savvy fugitive who becomes Mito's reluctant ally, delivers some of the novel's funniest lines while serving as exposition machine for the technological aspects of the plot. Detective Hiyama's rigid adherence to rules provides effective contrast to Mito's growing flexibility, though his character feels somewhat schematic.

Thematic Richness and Philosophical Depth

Seesaw Monster succeeds most completely in its exploration of how conflict can be simultaneously destructive and creative. The children's book collaboration between Miyako and her mother-in-law suggests that opposition itself can generate beauty, while the technological cat-and-mouse game in the future timeline demonstrates how conflict drives innovation and adaptation.

Isaka's meditation on memory and truth proves particularly compelling. Mito's discovery that his memories of the childhood accident may be fundamentally distorted raises questions about the nature of identity and responsibility. If our understanding of formative events is unreliable, how do we construct meaning from our experiences? The novel's suggestion that multiple versions of reality can coexist simultaneously feels both philosophically sophisticated and dramatically satisfying.

The surveillance theme resonates powerfully in our current moment, though Isaka avoids heavy-handed commentary. Instead, he focuses on how constant monitoring changes human behavior and relationships. The world where only handwritten messages provide privacy feels like logical extrapolation rather than dystopian warning.

Literary Ambitions Versus Genre Expectations

Seesaw Monster represents Isaka's most literary work, prioritizing thematic development over pure entertainment value. This shift will likely divide readers familiar with his more straightforward action novels. The philosophical weight occasionally threatens to overwhelm the narrative momentum that made works like Bullet Train so compulsively readable.

The novel's exploration of mythological themes positions it more clearly within the tradition of contemporary Japanese literature that blends realism with supernatural elements. Authors like Haruki Murakami and Banana Yoshimoto have explored similar territory, though Isaka's approach feels more systematic and less dreamlike than his literary compatriots.

Minor Flaws in Major Ambitions

Despite its considerable strengths, Seesaw Monster suffers from several structural and conceptual problems. The dual timeline structure, while thematically appropriate, creates pacing issues that prevent full emotional investment in either storyline. The mythological elements, while fascinating, never quite achieve the resonance that would elevate them from clever plot device to profound truth.

The novel's ending, while providing narrative closure, feels somewhat anticlimactic given the build-up of ancient conflicts and technological conspiracies. Isaka seems more interested in exploring his concepts than in providing the explosive resolution his previous works have delivered.

Some supporting characters feel underdeveloped, particularly in the future timeline where the conspiracy elements sometimes overwhelm character development. The balance between action and reflection that Isaka has mastered in previous works occasionally tips too far toward contemplation.

Final Assessment

Seesaw Monster stands as Kotaro Isaka's most ambitious and uneven work. While it doesn't achieve the perfect balance of entertainment and depth that characterizes his best novels, it succeeds in expanding his thematic range and demonstrating his continued growth as a writer. The novel's exploration of inherited conflict, technological surveillance, and the creative potential of opposition provides rich material for contemplation, even when the execution doesn't quite match the conception.

Sam Malissa's translation ensures that English-speaking readers can fully appreciate both Isaka's linguistic playfulness and his philosophical seriousness. Despite its flaws, Seesaw Monster confirms Isaka's position as one of contemporary crime fiction's most intellectually adventurous practitioners.

In an era where genre boundaries continue to blur, Seesaw Monster represents a meaningful contribution to the conversation about how popular fiction can address serious themes without sacrificing its essential entertainment value. While not entirely successful in its ambitious goals, it suggests fascinating directions for Isaka's future work and provides plenty of material for readers willing to engage with its complex ideas.

[Mylove4book · Rating 5 out of 5]

這本誠心推薦人妻閱讀XDDDDD山與海的距離啊XDDD

[mollie · Rating 5 out of 5]

This book is two books in one which StoryGraph does not say but alas, technically they connect but they still exist on their own as well!!!


The first half of this review is for SeeSaw monster.

Great book as always from Kotaro Isaka! It was actually a very refreshing change. I feel as though with “The mantis” it lacked something, the family angle wasn’t as good as it is in this one. The mother in law and the wife being in a dispute, the political comparisons etc to describe their relationship, all very good! The whole added part of the wife’s former career as an agent was amazing, I really adored the way in which her story was told.
The twist with the mum was unexpected! I really enjoyed that angle. I like that their bond remained distant afterwards, one similar former career did not make them best friends and I really really appreciated that as that can tend to happen in books.
I really enjoyed the husbands plot as well, it really had me at the edge of my seat! It was a rather unexpected twist, the suicide scene felt reminiscent of “Three Assassins” particularly the storyline of “The Whale” and I enjoyed all of it.
Overall, another great read.
Perfectly paced and I could not put it down!

Next review is for Spin Monster:

I won’t lie, this one may be one of my favourite pieces by kotaro isaka. It’s truly an amazing piece, it’s better than Seesaw Monster yet they work well together. Imagine my shock when I’m halfway through Spin Monster and realise that the books are like intertwined! Good lord! Spin Monster set far after Seesaw monster of course, given that the wife from Seesaw monster is the author of the snail book in Spin Monster. Wow. The mention of the mountain and sea people, the insurance man etc. such fun touches, so subtle yet it works. I read SeeSaw Monster first and then Spin monster, I feel like this order is best as to enjoy it more! I really truly loved Spin monster. It’s a masterpiece, I really didn’t expect what was coming and the writing was amazing as always. The slow subtle hints at the reveals worked very well, it felt maybe a bit empty towards the end yet it still worked. The unreliable narrator part with Mito worked very well like, I’m unsure if it’s even really unreliable narrator or what but it’s well done.
The use of AI as a “spin monster”, falsifying so much. Not being used as world building but as this man made horror or whatever, it’s really something unique. Usually it’s simplified down to a device for world building but that is certainly not the case here, anti-ai is very strong.

Seesaw monster referenced “going to japans tomorrow” or something similar, similarly to in spin monster when someone references “going to japans future” whilst on the train. Small little connections like this throughout the book really helped to connect the books together. The mountain and sea people etc. I really enjoyed them.

Overall, I feel like this may be one of my favourite Kotaro Isaka books. It truly had me gripped from the start, it’s a refreshing read? It’s something far different from his other ones yet it’s still his amazing book! Wow! I really recommend this one, it’s an amazing read and stands separate from the assassins series. It’s brilliant, I really enjoyed it and I hope he creates more books set in a sci-fi future. God damn I love his books.
“The future isn’t built on facts and data alone. There’s also human emotion”.

[Get Your Tinsel in a Tangle · Rating 4 out of 5]

Seesaw Monster is what happens when Kotaro Isaka takes one look at domestic drama and goes, “Needs more espionage.” And somehow, it works. I was expecting a slightly spicy family feud, not a whole mythological beef between Sea People and Mountain People turning your in-laws into Cold War assassins. But here we are.

The first half is peak '80s Japan, capitalism chic with a side of slow emotional death. Poor Naoto is just trying to sell pharmaceuticals without his soul falling out, but instead he’s stuck as the human rope in a mother-in-law tug-of-war between Miyako (his wife) and his actual mother, both of whom might be sleeper agents with blood vendettas going back generations. Honestly, by page 30 I was ready to throw hands on Miyako’s behalf, because this woman is fighting both domestic patriarchy and ancestral trauma before breakfast. Also, she writes a children’s book about a snail that might be a divine weapon and I want to marry her.

And then... plot twist! We slam-cut to a near-future Japan where AI is watching your every move like a digital Big Brother with a Ring cam obsession, and paper couriers are the new black market. Enter Mito, who is somehow both deeply paranoid and a hot mess, and Kagetora, his childhood trauma twin turned frenemy. These two are tangled in a passive-aggressive spiral of distrust that feels like The Social Network but with more knives and less Zuckerberg. Their story is way more tech-thriller energy, but still deeply weird in that delightful Isaka way. Think: facial recognition surveillance plus petty vengeance equals surprisingly heartfelt tension.

What makes the whole thing sing is how these two stories, wildly different in tone and setting, orbit the same weird gravitational center. The idea that conflict is inherited, like your mom’s nose or your dad’s inability to process emotions. Whether it’s a MIL-DIL blood feud or two men doomed to mirror each other forever, Isaka wants us to ask, are we cursed to repeat history, or just bad at therapy?

Also, credit where it’s due: Sam Malissa’s translation slaps. The pacing never stalls, the jokes land without being cringe, and the tonal whiplash between slapstick and sincere hits just right. One minute you’re laughing at someone trying to break into a safe with a rice cooker, and the next you’re grieving the emotional void between generations. It’s chaos. It’s perfect.

This isn’t a straight thriller or a mystery or even a sci-fi dystopia. It’s a genre chimera with cool sunglasses and unresolved mommy issues. And if you’re expecting everything to tie up with a bow, lol. Isaka leaves just enough open threads to make you spiral in the best way. Did the ancient war end? Is destiny real? Was the snail God? Who knows. Do I care? Also no.

Solid 4 stars. Minus one for the occasional “wait, who are we mad at now” confusion, but it earns its chaos stripes with style.

The Ancestral Beef Lifetime Achievement Award: For Services Rendered in Petty Vengeance, Cold War Chaos, and Multigenerational Spy Drama.

Huge thanks to The Overlook Press and NetGalley for the ARC. Y’all really said, “Would you like a mother-in-law spy thriller with intergenerational curses and zero chill?” and I said, “Yes, immediately.”

[Alex · Rating 4 out of 5]

I went into this book blind but it wasted no time in hooking me. I have seen the movie Bullet Train, but it’s my first book by this author. Sure, they don’t bother to provide a backstory for what’s happening, but that just leaves room for the excitement upfront. In a way, it’s not bogged down by the need to have an explanation for everything, which leaves no room for your mind to poke holes. It’s a recreational read instead, it goes down easily.

Interwoven with the action is the core plot of a daughter in law and her mother in law locked in an eternal feud, and the dynamics that play out over the family. This was unique and intriguing, adding enough tension but lowering the stakes from the other plot line. The two sides balance each other well and create a good push and pull that keeps the story going and the reader turning pages.

If you’ve seen the movie Bullet Train, you kind of know what to expect. There’s a little bit of the John Wick action in it if you let your mind fill in the blanks.

The story came together after a few twists, and then I discovered the book is actually 2 separate stories linked together by a few things, including the theme of how two people can be linked together through destiny, for better or for worse.

The second story is actually set in the future in a lightly sci-fi setting, with a bit of new tech. Nothing like a Blade Runner, but enough to keep it interesting. This second story was even more intriguing than the first, with a few different elements adding to the mystery up front. As the story went on it became a bit convoluted for my tastes. If the book had committed from the start to tying up the threads of the story tightly and making sure everything had a reasonable explanation, I think I would have had more patience for what the end was trying to do.

Overall though, I enjoyed it, 4/5 stars.

*An uncorrected proof of this book was provided by the publisher at the reviewer’s request in exchange for a fair and uncompromising review.

[Ema · Rating 4 out of 5]

Seesaw Monster by Kotaro Isaka is divided into two sections with very different themes, yet they’re deeply connected in ways that only become clear as the story unfolds.

In the first part, Naoto Kitayama’s mother lives alone after her husband’s death. Worried about her, Naoto moves in with his wife, Miyako Shiota. From their first meeting, Miyako and her mother-in-law, Setsu, clash endlessly. What begins as a domestic drama soon turns dark when Miyako, a former secret agent, starts suspecting her father-in-law’s death wasn’t natural and that her husband might be framed in a work-related fraud.

The second part, Spin Monster, shifts to a futuristic Japan driven by advanced technology. A tragic accident leaves one boy as the sole survivor of two families, raised by grandparents Naomasa Mito and Kagetora Hiyama, who share no bond despite their shared loss.

Fast forward, when an AI creator is murdered after sending a mysterious message through Mito, he becomes entangled in a dangerous conspiracy that could spark a war. Hiyama, now a police detective on the case, crosses paths with Mito once again. To my surprise, Miyako, now known as Miyako Setsu, a celebrated children’s book author in her nineties reappears, tying the two worlds together in an unexpected way.

Here, AI doesn’t just think, it feels, possessing an uncanny intuition that can predict and possibly manipulate future outcomes, posing real danger to humanity. Compared to the first part, this section is far more complex and layered, filled with unreliable characters and shifting truths. A mix of family drama, mystery, and sci-fi thriller, Seesaw Monster is both emotionally charged and intellectually gripping, an inventive exploration of human connection, suspicion, and the cost of progress.

[wally · Rating 3 out of 5]

finished 25th october 12025 good read three stars i liked it no less no more your mileage may differ kindle library loaner first from isaka and i will read more from isaka given time and place...usually i'm not inclined to read sci-fi...i do like sci-fi, there's come great sci-fi i've read...canticle for leibowitz comes to mine...others...i hoped for a different ending one i tried to imagine as the story made its way and reached a conclusion that was unsatisfactory. does that mean the story lacks? not at all. cold be a reflection of our society, our times...nihilism...but nihilism regardless.

thought it was an intriguing and well-told story...actually, stories, this is two novellas and perhaps that is telling enough. evolution, it you want, if you demand, as social and fashionable engineering calls for so say we all, verily, hallelujah, now and forevermore. we love our team!

so...what? i'd hazard that if you accept the cards dealt then all is well and all manner of things are well. go along to get along. or don't. in the end, what matters?

interesting, what the story might say about memory, having come off a recent read about...the plot, the sequel, as in, whose memory and whose memory is it? in this story, your memory? or the machine's? or something else.

so...so i'll loo for ore from isaka...there was a...thing...a piece of another story here and though i did not read it i will read more from isaka. good enough for you? cue the soundtrack. go on, take the money and run!

[Liong · Rating 4 out of 5]

When I picked up this book, I only knew one thing: the author is the brilliant mind behind the Bullet Train Novel. Yes, that action-packed 2022 Hollywood movie is full of chaos, charm, and wild surprises. I originally set the book aside, thinking I'd get to it later. I really should’ve read it sooner!

Now that I’ve finally dived in, I’ve discovered it contains two stories—seemingly unrelated at first, but deeply connected in surprising ways. (A science fiction story) 🧐

The ride? An absolute roller coaster. Packed with action, unexpected twists, and a ticking-clock intensity that keeps you turning the pages. 😅

It’s a world of spies, secrets, and high-stakes missions, where you're constantly left wondering: What’s going to happen next?

Told across two different time periods, the narrative slowly weaves together into one satisfying, clever whole. Trying to piece it all together is half the fun.

At its core, this book is about relationships, particularly the intense, complex rivalry between a wife and her mother-in-law. It’s messy, human, and totally engrossing.

In short, this book is thrilling and smart from start to finish. A fantastic, fast-paced read that doesn’t forget to have heart.

[Sapphire Detective · Rating 4 out of 5]

Since this is an anthology, technically, I presume people would expect me to highlight one of the other here. But, in reality, these two stories are not only both equally good, in my opinion, but too intertwined to consider them separately. Both dealing with the internal nature of why we as humans are prone to fighting, and prone to falling into the mindset of "us vs. them" mentality. It doesn't really present an answer one way or the other, per se, but does try to say that fate does not always have to play as it wants us to. Seesaw Monster is supposedly going to be adapted in the next few years, but I'd almost rather see its companion story here, Spin Monster, and its AI controlled dystopia. Or. at the very least, they could have both stories present in the same film--like I said, the two are more intertwined than it would seem, and not just thematically. Either way, both are worth the read, even if Spin did make me despair for humanity a bit.

Seesaw Monster - 4.5/5
Spin Monster - 4/5

Overall rating: 4.25/5 (rounded down)
Would I own/re-read?: Probably!
TW: Conspiracy, Death, Murder, Terrorism, Dystopia (Spin), Torture (Seesaw)
Does the animal die?: No animals are directly harmed in either story, to my memory.

[Daniel Allen · Rating 2 out of 5]

Two loosely connected espionage stories. In the first, Seesaw Monster, a young married woman suspects her mother-in-law may be a murderer. The woman will rely on her training and contacts as a former secret age to investigate. In Spin Monster, a courier becomes enmeshed in a mission to defeat a nefarious AI threat.

Sterile writing, overflowing with stilted dialogue. The characters and the overall stories are lifeless. This came as a surprise, as I was drawn to this novel because the author wrote Bullet Train. Having only seen the movie, maybe that novel would have also had the same failings. I felt like I was kept at a remove from the characters in both stories. There may have also been a "lost in translation" aspect to my lack of enjoyment of this book. The perfect example was the constant harping on the "sea vs mountain people" and later the "scale insect vs ladybug" metaphors. These were confusing as an American reader, and were belabored. Another issue that I had with the text was that it was sometimes difficult to know which characters were speaking within scenes. I won't be seeking out further writing from this author.

[Viva · Rating 3 out of 5]

Edit: This is actually a book of two short stories that are somewhat related to each other.

Spoilers ahead. Surprisingly this is a book of short stories.
Seesaw Monster: Generally easy to read and follow. The pace of the story was slow and never really picked up but the characters were fairly interesting and I followed along. I didn't like the unannounced changing POV that changed between wife Miyako and husband Naoto. The setting is the couple living together with Naoto's mother (called Mother in the story) and the undercurrent of animosity that ran between mother and DIL.

Naoto is a pharmacy/drug salesman and he is suddenly given a large account, supplying drugs to the O. Hospital. All he needs to do is to entertain the O. Hospital executive, ie. keep him company and go with him to bars and clubs. About 1/2 way into the story he finds that O. Hospital has been engaging in insurance fraud and his co-worker Watanuki has been complicit. Watanuki kidnaps him, told him that he should have shut his mouth and done nothing. Now Watanuki is going to kill him and make it look like a suicide.

Meanwhile, Miyako is getting suspicious that Mother had previously killed her own (Mother's) parents and Naoto's father for insurance money after finding out that many people surrounding Mother were dead from suspicious circumstances. We also find that Miyako is a retired secret agent in Japan's secret service and is using her old contacts to investigate Mother.

While Watanuki prepares Noato for suicide, he allows him one last call to Miyako. Miyako quickly traces the call and arrives at the place where Naoto was held. She quickly fights and puts down 2 thugs but they say that Naoto has already been taken away to be dispatched. When she runs downstairs, one of the thugs get in a car and run her down. Now wounded, she is unable to fight the thug. Miraculously Mother arrives. It turns out she is also a retired secret agent. She quickly overcomes the thug and tortures him to reveal where Naoto is. Together Miyako and Mother save Naoto.

Mother explains that she could tell that Miyako was a retired agent too and knew that Miyako was investigating her. The truth was that the enemy had killed her parents and husband as revenge. The story ends with Miyako and Naoto moving out of the house and living separately from his Mother.

OK, now I've finished reading the second story and remember why I didn't really like this author. Story 2 is set way in the future when technology in some ways is more advanced. They have self driving cars and pass cards, I mean we have them too now, but the ones in that future are more advanced, perform better and can do more things.

Anyway, it's a story that is needlessly confusing told with characters that are needless. There are 4 protagonists, sort of. Two of them are smart and one of them dies early on but he has given instructions to the other smart one and one of the others to destroy AI which he feels will go out of control. The other 2 are kind of along for the ride. After finishing the story, I'm not even sure what happened. The end.

Oh, and they are connected because Miyako is in this story as well, except she's very old.

[Claire · Rating 3 out of 5]

I am not certain which story you are supposed to read first. Seesaw Monster or Spin Monster.

I read Spin Monster first and I am glad I did. While Seesaw Monster was good, I do think Spin Monster was better. More intrigue. The overarching idea across the two stories is about people that are Sea people or Mountain people and the conflict that occurs when the two come together, which I think is fascinating. While reading Spin Monster, I guessed (wrongly!) that the AI was in the car and that's what caused the accident but I loved the reveal both that he has been used in human experimentation and has a camera in his eye and when he sees that he was the cause of the accident although was I was writing that out, how could there be footage of the accident if he only got the camera in his eye after the accident because they used him because he had no family to consent to the human experimentation… his memories are wishy washy… did I miss something or is there a gap there?

So if I really think about it, reading Spin Monster first is the way to go as the main character shows up in this story and then reading Seesaw Monster, you get her back story.

[Katie · Rating 4 out of 5]

I had no idea what I was getting intoーwith a title like that!ーand I couldn't put it down. Two interconnected short stories, right after the other, generations apart but uncannily similar.

I must admit that I hated the ridiculous hatred between the first two ocean/mountain dyads, which is the stereotypical wife and mother-in-law setup. The second one was bland, basic high school boys as rivals, you can find in any manga.

But the espionage backdrop was a blast and totally unexpected. I enjoyed the contrast between the analogue of today and the imagined near-future technoscape, where AI seek to control us not through violent action, like in so many movies, but misinformation.

The translation is superb. I read a fair amount of translations from Japanese to English and they're usually so clunky, awkward, and direct to the point that I can guess at the original literal Japanese (not a good look).

Thank you to Edelweiss+ and the Overlook Press for the advance copy.

[claudia reads it all · Rating 4 out of 5]

I am so glad I get along well with my mother in law. I kept thinking that during the first part of this book, which centers around Miyako and her MIL, who most definitely do not get along. Every day they bicker and throw spiteful barbs at each other while Naoko, the husband and son, respectively, deals with some unethical and possibly illegal happenings at work. There are many other secrets, however, and when Naoko's life is in danger, the two women must get over their differences - which may be the result of ancestral strife - if they are to save him.

The second part takes place a few decades later, in an AI-dominated near future, where the most secure form of communication is good old pen and paper. The ancestral form of strife is still in play, much like a character from the first novella.

I enjoyed this book so much - I loved the movie Bullet Train and this had much of the same vibe, especially during the very cool fight scenes.

[BaiLing · Rating 3 out of 5]

這是作者應出版社之邀，為慶祝創立130周年，和其他七位小說家，撰寫從原始到未來各個時代的故事。貫穿其間的中心主旨是「人與人之間的對立」，並創造出有淺藍色眼珠的「海族」與有著大耳朵的「山族」，並沿著「海族與山族的後裔注定會互相對立」的概念，寫出分別發生於「昭和泡沫經濟」時期的1988年，和「近未來」時期的2050年的兩段故事。

《蹺蹺板怪物》。身為特種部隊的優秀情報員的宮子，在一次出任務時認識了平凡卻溫柔的直人，之後退休與之成婚，但不知怎地，卻和婆婆無法和平相處，動輒得咎的結果，幾乎天天上演婆媳大戰。直到直人被職場前輩陷害，成為向醫療機構行賄的替罪羔羊後，兩個女人聯手救人，宮子才發現眼中的惡婆婆，不但是同個情報單位的前輩，她們兩人更是分屬山族和海族的後裔，先天就注定要水火不容的。

《旋轉怪物》。2025年，由AI控制的世界，所有的隱私、秘密無所遁形。於是興起了「信差」的職業—可以把用紙筆書寫的秘密，交由信差人力送達收件者。

水戶直正是個獨立信差，在一次前往北海道送信的新幹線上，有位陌生男子忽然在鄰座坐下，交給他一個薄薄的信封和厚厚的酬勞，要他在仙台下車送信給昔日好友。男子交代完後沒多久，在大批警力的追捕下，居然就從急速的火車上跳下身亡。

原來男子要水戶去找的人是昔日一起開發出AI的同伴，果然一如當初同伴的預言，在AI全面掌控下的便利生活，得付出出賣了靈魂自由的代價。水戶成了要一起執行毀滅AI的同夥人，而一路追趕他們的警察中，有從小便互看不順眼的同學檜山。

自殺男子給的暗示，是要他的夥伴去找一位舉世聞名但現已隱居的童書作家老婆婆，她的名字叫宮子……。

就這樣，2025年的故事就和1988年的故事連在一起了。

水戶和檜山是海族和山族死對頭的關係還是重點，至於AI有被消滅嗎？眼見不一定為憑的世界裡，資訊可以捏造，記憶可以扭曲，多數不會是正確，少數從來不是錯誤。真相，永遠是在遙遠的未來，等待是唯一的途徑。

真不想期待的2025年啊！

[Ailin · Rating 4 out of 5]

4.25 stars, rounded down.

I really enjoyed this one. I've seen Bullet Train but never read anything from Isaka before and was pleasantly surprised. Although the set ups of mother/daughter-in-law feuds and school boy secrets are basic plot set ups, I was engaged with the prose (which I think is large in part to a great translation -- many Japanese books can come off stilted when translated to English) as well as the addition of espionage.

Two novellas back to back with mostly different characters, but some connection between the two explored themes of familial relations, AI, and trust. The characters were likable and the tone was serious as well as comedic at times. Worth a read -- check it out in July!

Thanks to NetGalley, the publisher the author/translator for an eARC of this in exchange for an honest review.