Jump to ratings and reviews
Rate this book

A Sinner of the Deep Sea

A Sinner of the Deep Sea, Vol. 1

Rate this book
The ocean covers about 70 percent of the earth’s surface―a whole world, yet unknown to humanity…and in its depths a nation, thousands of meters beneath the waves. There, the mermaid Jo has been whiling away her days in peace. But that tranquility is shattered when her friend Ryuu is imprisoned for breaking the gravest of undersea laws: Their existence must be kept hidden from the people above. But why would Ryuu let the secret slip? And who did she tell? The curtain rises on Jo’s adventure to save her friend―and on a story of love…?!

178 pages, Paperback

First published June 18, 2024

6 people are currently reading
216 people want to read

About the author

Akihito Tomi

14 books9 followers
AKA: Tomi Akihito, 冨明仁

Ratings & Reviews

What do you think?
Rate this book

Friends & Following

Create a free account to discover what your friends think of this book!

Community Reviews

5 stars
45 (19%)
4 stars
108 (46%)
3 stars
64 (27%)
2 stars
13 (5%)
1 star
3 (1%)
Displaying 1 - 30 of 44 reviews
Profile Image for Steph ✨.
684 reviews1,611 followers
July 31, 2024
I really enjoyed this. Love Jo as a character and excited to see where volume 2 goes.
Profile Image for Mark.
2,801 reviews269 followers
June 28, 2024
Jo is a free-spirited mermaid who does her own thing, which would probably cause more trouble except her friend Ryuu is there to save her. Until Ryuu does something truly heinous, revealing herself to a human, and Jo is forced to pick up the pieces.

It might have seemed a bit much having two mermaid books come out in a week, but this one and This Monster Wants to Eat Me achieve a happy coexistence by virtue of being nothing alike.

The other title is firmly occupying the horror mermaid space, while this one is a more adult fairy tale sort of thing that makes a heck of an impression right out of the gate.

First off, Jo is great. Beyond the clear love the mangaka has for depicting the female form (this is a book that loooooves hips), she has such a stubborn and steadfast attitude, especially towards Ryuu, that she’s a winning character.

By the time the book ends, you can see that this is going to be a real test of friendship (Jo already wins for sticking by Ryuu), that may become even more of a test than either of them realizes. Hopefully.

Really it’s a lot of scene setting to start, but it’s very engaging scene setting. As somebody who is firmly neutral on the subject of merfolk, both these new manga use that legend to excellent effect.

A lot of the stuff in the merfolk world here could seem incredibly hokey, but it’s well realized and it’s obvious that some genuine thought has been put into it. You could probably write an entire review breaking down how the standard of fashion works in this realm. It’s fascinating stuff.

There’s an elegance here to how it introduces these characters through their actions and we learn about them before they rapidly change. Ryuu is a famous dancer who is self-admittedly sleeping her way to the top, but her encounter with the human world turns her entire life on its head.

And what we see of the human world is really neatly imparted. Just enough to set the time and place and move on, while also allowing for the requisite bikinis such a setting requires.

Yuki, the human Ryuu falls for, isn’t precisely what you’d think of when you imagine a guy who’d capture a mermaids heart, but he’s a lot more interesting because of that fact. He’s a dork for undersea creatures who hates being on the ocean, plus he has a sister and brother-in-law to bounce off. It’s a good establishment of his character.

This pretty much works the whole way through, from Jo’s elegant opening sequence to the rapid escalation of stakes towards the end that promises more trouble for all concerned as the tide (cough) of public opinion shows how fickle people are and who’s actually your true friend.

4 stars - a very strong start that promises good things ahead. The rare case where two very similar books went head to head and I think both of them have a lot to recommend them.
Profile Image for ˙⋆✮ Anny ✮⋆˙.
569 reviews299 followers
August 6, 2025
That cover screams "The Little Mermaid" which is my favorite Disney movie so I HAD to pick it up. You know, it's about mermaids and a strong female friendship, I HAD to.
The art in this is gorgeous to look at, the first chapter barely has any text and it still tells us so much about our main character Joe.
The story starts slow but by the end of this volume, I found myself hooked and I definitely wanna know what happens next.
The whole "mermaid falls in love with a human" isn't new, the human in question seems like a sweet guy though.
Profile Image for Annina Seiler.
91 reviews1 follower
July 4, 2025
Mein zweiter Manga und ich habs richtig geliebt!

Erstmal vorweg: Ich bin ein riesiger Meerjungfrauen Fan. Das Cover ist mir deshalb sofort ins Auge gefallen und der Klappentext hat mich schlussendlich überzeugt. Es war ein Spontankauf, der sich mehr als gelohnt hat. Joe und Ryu sind vollkommen gegensätzliche Meerjungfrauen und doch beste Freundinnen: Joe, die Aussenseiterin, die sich nicht um die Meinungen anderer schert und Ryu, die beliebte Tänzerin, die einen reichen Freund nach dem anderen hat. Die Zeichnungen der Unterwasserwelt sind sehr gelungen und in wenigen Bildern kriegt man einen guten Überblick über die Welt des Meeresvolkes, sieht wie sie leben und welche Gesetze herrschen. Und welche Konsequenzen ein Verstoss nach sich zieht… Nach dem fiesen Cliffhanger am Ende bin ich nun mehr als gespannt, welchen Masterplan Joe aushecken wied, um Ryu aus ihrer verzwickten Lage zu helfen.
Profile Image for Maja.
306 reviews35 followers
October 18, 2025
Nakon druge preporuke odlučila sam da dam šansu prvom broju — i već sutradan sam progutala čitav serijal od tri toma. Savremena avantura koja na maštovit način reinterpretira Andersenovu „Malu sirenu“. Posebno bih pohvalila crtež koji ubedljivo prenosi emocije likova i čini priču živom i opipljivom. Šlag na torti mi je bio negativac koji maestralno izvrće dešavanja kako bi dalje destabilizovao podvodno društvo i manipulisao ga u željanom pravcu. Sve to, nekako, zastrašujuće poznato.
Profile Image for Lucille.
1,466 reviews276 followers
September 14, 2023
Franchement ça aurait presque pu être un 4,5/5 car j’ai beaucoup beaucoup aimé mais un peu saoulé des nombreux plans boobs 😅
Il ne se passe pas grand chose à part nous exposer le monde des sirènes, le tout début est très beau avec Jo l’héroïne qui joue avec un bébé baleine. Vraiment un tome d’exposition jusqu’au dernier quart où l’histoire se déclenche enfin. En vrai j’aime vraiment beaucoup l’héroïne qui est très cool et les dessins très beaux mais bon à voir la suite.
Profile Image for Jeanne.
140 reviews12 followers
September 6, 2023
P T D R LE SCENARIO
Je met deux étoiles parce que j'aime les poissons <3 C'est tout
Profile Image for Neshia.
375 reviews
June 10, 2024
Thanks Edelweiss for the ARC. This was a great! I can't wait to purchase it for my library and recommend to my patrons. I loved it and I think they will too! I enjoyed the plot and can't wait to see where the next volume takes me!

You never know what is going to be found in the depths of the ocean and when a mermaid falls for a human, her friend Jo, must find a way to help her escape. The number one rule in the sea is to keep humans from discovering that mermaids exist and Ryuu just broke it.
Profile Image for Aura.
106 reviews12 followers
September 11, 2024
Came for the gorgeous art, stayed for the intriguing world and story. This is giving me similar vibes as Kaoru Mori and Aki Irie's works and I'm a fan. Can't wait for the next volume!
Profile Image for Elizabeth Knowles.
95 reviews7 followers
May 11, 2025
This was such a delight! Ryuu is an absolute cutie—I want to wrap her in a blanket and protect her at all costs. And Jo?? JO?? Stunning, powerful, effortlessly cool… I’m in awe. She’s giving main character energy in every panel. 😍🔥
The art is gorgeous—seriously, every page is a visual treat. And the comedy? Pure gold. I was laughing out loud and smiling the whole way through. It’s a quick, feel-good read that’s perfect for breaking a slump.
Definitely continuing this series. If you love charming characters, good laughs, and beautiful art, this one’s for you! 💫📚
172 reviews
July 23, 2024
I wanted to like this more than I did, to be honest. The art was nice, until it decided with each female character to do a boob shot, and often a 'thigh' shot as well, as if that was needed at all. I just didn't find the story compelling. Jo's friend Ryuu is a serial dater, and described to be a gold digger. She falls in love with a human despite being implied to have only met him once. Jo clearly disapproves, but promises that she'll get Ryuu out of prison to see this man? I wanted to know more about the mermaid society, as there were glimmers of interesting background and characters. It just felt kind of empty, with no particular depth to it.
Profile Image for S.Q. Eries.
Author 7 books15 followers
August 6, 2024
In Summary
If you’re searching for artwork beautiful enough to drown in, take a look at A Sinner of the Deep Sea. The plot of this The Little Mermaid reimagining is off to a slow start, and the motivations of our main character Jo remain a puzzle. However, this ocean fantasy contains breathtaking natural scenes and an entertaining merfolk world.

The Review
Thousands of meters below the ocean surface is The Abyss, a massive underwater cavern that is home to a nation of merfolk. They once occupied the shallows, but with the advent of human ships and the brutality they brought, the merfolk withdrew to the deep and forbade all contact with humans. For the mermaid Jo, following that grave law is common sense. However, her world gets turned upside down when her best friend breaks that law by falling in love with a human.

This story is a modern-day reimagining of The Little Mermaid – that is, if the Little Mermaid had a tough, protective friend. Jo is the main character of this manga, but she’s not the one falling in love. Forget humans; this brusque underwater lone wolf is antisocial among her own people. Her only soft spot is for her friend and polar opposite, Ryuu. A celebrity dancer, Ryuu uses her looks and talent to climb the merfolk social ladder. For her, men exist solely for the purpose of being seduced for all they’re worth. But all that changes when she meets and falls in love with a human on the seashore. Caught in the act by The Abyss’ border patrol, Ryuu gets locked up because she refuses to renounce the human, and that’s when she turns to Jo for help.

The storytelling is a bit unusual. Thus far, we know precious little about Jo, but there is a ton of information about Ryuu. Moreover, Ryuu’s the one who has very concrete goals, and she’s the one who instigates the primary conflict of the story. Meanwhile, Jo’s simply floating along in life, and we don’t even know why Jo chooses to be friends with Ryuu. The narrative hints that we’ll get more information about Jo in Volume 2, but for the moment, all we know about her is that she doesn’t care about fitting in in society and that she cares very deeply for Ryuu.

The pacing is quite slow. It’s not until Chapter 3 that things start happening plot-wise. However, what Tomi-sensei does instead is immerse readers into the world beneath the sea. The first 32 pages, which are dedicated to an ocean frolic Jo has with a baby whale and its mother, have almost no dialogue. The next 25 pages are dedicated to showing the society within The Abyss. It’s a lot of pages used to establish setting, but Tomi-sensei turns it into a visual feast. All the ocean creatures, seafood items, and natural structures are drawn with realistic detail. As for The Abyss, it is a lively town with expressive characters and undersea versions of modern eateries, agriculture, fashion, and living spaces. But whether it’s the striations of a salmon steak, the markings of a sea slug, or the accessories adorning the merfolk, the illustrations are a delight for the eyes. Although this is a fantasy and not a slice of life, I find Tomi-sensei’s style and character designs highly reminiscent of mangaka Kaoru Mori (Emma and A Bride’s Story)

Extras include translation notes.

For more manga and book reviews, drop by my blog Keeping It In Canon!
This entire review has been hidden because of spoilers.
2,045 reviews20 followers
July 31, 2024
Surprisingly there's still not that many mermaid themed mangas out there - Recently we've had In the name of the Mermaid Princess, but otherwise we're reaching back to Mermaid Melody Pichi Pichi or Moonchild (I'm exlcuding all the one-shots and yaoi titles) but for actual, fish tailed mermaids, the pickings are quite scarce, so I was delighted when I saw this in Forbidden Planet.

The story follows sarcastic mermaid Jo who discovers that her flighty best friend has fallen in love with a human and risks exposing the mermaid community.

What I really liked about this were the mermaids - Jo and Ryuu are mermaids with attitude - hard drinking, sarcastic and they seem like real women, as opposed to fairytale constructs. Supporting cast are solid too - Yuki the love interest isn't your usual pretty boy, he's geeky with floppy hair and glasses. We get a decent amount of background on him, with his sister and adventurous brother-in law. Loved the snooty waiter in the mermaid restarant too.

I like the story so far too. Its refreshing that it's not the protagonist who has fallen for a human but her best friend. So we get an extra friendship theme dynamic.

Artwork isn't bad, its not beautiful, but it reminded me a lot of manga in days gone by. The opening with the whale for example reminded me of Tezuka's Triton and there's a nice nostalgic feel about this, which contrasts with the unusually realistic characters, and level of detail.

From a massive mermaid fan POV, there's also plenty of mermaid action. Its nearly all set underwater so there's lots of tails, swimming and underwater city worldbuilding.

Have to say I was pretty impressed with this one.
1,367 reviews5 followers
June 26, 2025
POPKULTUROWY KOCIOŁEK: Manga Grzesznicy lazurowej otchłani autorstwa Akihito Tomiego to trzytomowa manga, która przenosi czytelnika do fascynującego świata syren. Te mityczne istoty żyją głęboko pod powierzchnią oceanu, w społeczeństwie izolowanym od ludzi i opartym na surowych zasadach. Kontakt z człowiekiem jest tam zakazany, a złamanie tej reguły grozi surowymi konsekwencjami. To właśnie ten zakaz staje się osią fabularną, gdy syrena Ryu zakochuje się w człowieku imieniem Yuki. Za swój czyn trafia do więzienia, a jej los spoczywa w rękach przyjaciółki Jo – zbuntowanej, silnej bohaterki, która nie cofnie się przed niczym, by ją ocalić. Ta opowieść to więc reinterpretacja baśni Andersena z społeczno-politycznym przesłaniem i nowoczesnym rysem emocjonalnym.

Jedną z największych zalet mangi Grzesznicy lazurowej otchłani są bez wątpienia rysunki. Styl graficzny Akihito Tomiego urzeka od pierwszej strony. Kreska jest pełna gracji, detalu i nastrojowości, która doskonale oddaje atmosferę podwodnego świata. Autor mistrzowsko wykorzystuje przestrzeń i ciszę – niektóre sceny są pozbawione dialogów, ale jednocześnie przepełnione emocjami. Długie, kontemplacyjne sekwencje stanowią tu wizualne preludium do wielu dramatycznych wydarzeń. Szczególnie dobrze wypadają także projekty postaci, z Jo na czele – syreny o silnym charakterze i pełnej determinacji osobowości...

https://popkulturowykociolek.pl/recen...
Profile Image for Bethany.
866 reviews20 followers
September 29, 2025
Couldn't read a word of it. okay. I could, just a couple. Like her name which I'm pretty sure is Joe. Mainly because I could only find a German edition of it. Hopefully i can find an English edition. But the artwork was pretty good, and from what I could infer from the synopsis and the context clues, the story is pretty good as well. Honestly from the cover I thought this was a little mermaid retelling featuring Ariel. what can I say, I see a mermaid with that bright red hair and I think Disney's version.
In any case not a little mermaid retelling, Disney or the original. But it looks pretty interesting. I'm hoping to get a version I can read so I know what's actually being said. Although it is fun to make up dialogue as well.
I enjoyed the scenes of her swimming with the whales and of her being kicked out of the fine dining establishment by the maître de only for him to find out she was actually supposed to be there. Didn't need to understand the words for that one. It was funny regardless.
So recommended? probably. I can't really speak for the story or dialogue since I could only read words like hallo, danke and Joe. or exclamations.
Buy/Borrow? Borrow
Profile Image for Hilary Bull.
90 reviews1 follower
Read
July 1, 2024
The fan service I could have done without - we don’t need multiple close up frames of her chest and hips as character setup.
However, I frothed (like sea foam) the scenes of Jo as a tiny character in the vastness of the space. They were big moments of quiet, like Miyazaki’s ‘ma,’ that gave you an idea of who Jo is in her environment, her joy and sense of play, without necessarily moving the plot forward. I felt this especially in her swim with the whales and the enormity of the ocean that echoed across the page in large frames, juxtaposed by the restaurant scene, that bulged out in a clamour of crowd and clanking plates where her smallness wasn’t freedom and she didn’t quite fit.
One volume wasn’t enough to have me fully invested in their motivations, but definitely intrigued in their future character choices.
Profile Image for Jessica Walsh.
Author 9 books24 followers
September 24, 2024
We all know the story of the Little Mermaid, right? A young mermaid gets in trouble when she travels to the surface and a human man catches her eye. Then she gives up her tail and other important parts of her life just for love and to join him, with varying levels of success depending on which version you read. Somehow, recently, I’ve managed to read a lot of manga and graphic novels centered on mermaids and this is another with an interesting twist...

Read the full review at Well, Are They? A Queer Review Blog
https://wellarethey.blogspot.com/2024...
Profile Image for Salem Starlight.
9 reviews19 followers
September 4, 2025
So this is a quick read, I had forgotten how quick manga is to read, probably due to the pictures and all that. But it is a quick read, and a good one. I already want to read the next one and probably the whole series. Definitely worth it to anyone who likes stories about mermaids. It is about a pg-13 rating I would say, and it has an interesting headcanon on mermaids that doesn't deviate that much from the common tropes you typically see in Mermaid stories. It may be a bit before I get the others in the series though, but I'm willing to re-read this again once I do.
Profile Image for Rebecca.
4,320 reviews69 followers
June 16, 2024
What if the Little Mermaid was a serial dater and had a close friend who had to deal with the fallout of her ill-advised love affair with a human? Add in art that's reminiscent of Kaoru Mori's and this is looking like a winner. (I also love the worldbuilding which extends even to the clothing - for a merperson to be dressed, their chest and the place where fins meet human torso must be covered, regardless of gender.)
Profile Image for Cecille.
240 reviews2 followers
January 28, 2025
It may not be yuri, but it's gay to me goshdarnit!!

A volume full of spectacular art, lovely character designs, crammed with cool world-building details, all in service of telling this story between two very messy mermaids. This volume is a bit uneven in terms of pacing, with a lot of the story content backloaded in favor of large world-establishing panels in the first few chapters, but again, I really like the world being established here! Very excited to read more.
Profile Image for Carolina Gardner.
115 reviews11 followers
August 4, 2025
It’s been so long since I read an original story about mermaids! And this manga really takes the bar! I love the amazing illustrations and details of the characters and the world they live in, they are absolutely gorgeous.😍

Also, I love Jo’s character, she’s both beautiful and tough! And Ryuu is a total sexy queen🔥🤩 I am definitely hooked on this story and the characters so I can’t wait to read the next book.
Profile Image for Christina Mastoraki.
271 reviews
April 11, 2025
Δεν διάβασα τη σύνοψη και στην αρχή νόμιζα ότι ήταν ένα retelling της μικρής γοργόνας με βάση το εξώφυλλο. Καμία σχέση, αλλά δεν με απογοήτευσε. Το art style είναι υπέροχο και οι χαρακτήρες πολύ εκφραστικοί. Είναι λίγο φτωχό σε world building, αλλά από τα λίγα που λέει είναι πολλά υποσχόμενο. Η αρχηγός της φρουράς φαίνεται να είναι ένα βήμα μπροστά. Ελπίζω να υπάρχει αρκετό σασπένς στη συνέχεια.
Profile Image for D.T..
Author 5 books80 followers
January 3, 2025
I liked the friendship between Jo and Ryuu, and Jo herself. She's sure of herself and the more logical of the two. I liked the artwork, but many of the closeups for the female characters were unnecessary.

Profile Image for fairy._diary.
227 reviews
March 2, 2025
•piękny styl
•laska z czerwonymi włosami na ma na 100% crusha na tej drugiej i cierpi wiedząc, że jej uczucia nie są odwzajemnione
•typ w okularach???? So cute and pretty? Damn
•ta tancerka jest slay i silly w jednym momencie
This entire review has been hidden because of spoilers.
Profile Image for Paulette.
897 reviews2 followers
June 30, 2024
The artwork was beautiful, even with some scenes drawn more gratuitously than necessary. I wish the plot had kept up, but who knows, we’ll see what happens in the next volume!
Profile Image for Reby.
131 reviews
August 18, 2024
⭐⭐⭐⭐
Excited to see this series flourish.
Displaying 1 - 30 of 44 reviews

Can't find what you're looking for?

Get help and learn more about the design.