It is very likely that English-speakers will come to this light novel after having seen the film adaptation. There are some significant differences between the two, so knowledge of one doesn't affect the surprises (much) of the other. Still, the novel adds much of depth and interest to the film, so if you've enjoyed Fukada and Tsuchiya as Momoko and Ichigo, please be sure to read Takemoto's version of the story. I should add here that this may be the first book I have ever read that I literally could not bring myself to put down. I kept wanting to read more and ended up finishing it in one sitting. I have seen the film before reading the book, myself, and enjoyed the adaptation greatly, so I was perhaps predisposed toward this one, but I haven't had the same experience with any other book where I'd seen the film first.
To summarize the story without giving away too much, in rural Japan two young women who seemingly could not be more opposite meet by chance and become fast friends. As they grow to know and bond with each other, they face the same problems of uncertainty and awkward tentativeness that have been the hallmark of young people since the beginning of time. Obviously, this summary doesn't give a real sense of the specific events in the story, and it doesn't even touch on the techniques brought to bear by the author which tie the narrative into a thematic whole (watch for things that are doubles, for the repeated idea of collaboration between two as a bulwark against the multitude, and the providential role of accident especially). Now, with that aside, spoilers follow.
SPOILER-HEAVY EXTENDED SYNOPSIS
Momoko is a young, disaffected woman who is (similar to Chihiro at the beginning of Miyazaki's film Spirited Away) unable to participate fully in the flow of life. This is presented by her unwillingness and inability to form friendships, her disinterest at witnessing animals dying, her indifference to her parents' divorce, and so on. In Middle School, Momoko develops some interest in embroidery as a result of her fascination with the French Rococo period, the decadence of which she sees as a perfect fulfillment of her alienation. More importantly, she develops a love for the street fashion style called "Lolita", which is focused on extravagant decoration, frills, and lace (and, by the way, is entirely unrelated to the novel by Nabokov, a misperception that has led some Western critics to fundamentally misunderstand it). Her father, whom she calls The Loser, is a man who wants to do the best he can, but who is fundamentally lazy and so unable to do anything well. He tries to rise in the ranks of the organized crime families of Amagasaki, but when one of his schemes, involving using two brands together in counterfeit fashion items (an idea that he got from one of Momoko's fashion magazines) draws the ire of international corporations, he is forced to leave with Momoko to live in Shimotsuma, in rural Ibaraki prefecture, with his mother at her farm.
With this change of residence, Momoko finds that it is more difficult to get money from her father, now that he is not making as much selling counterfeit fashion items, so she casts about for new sources of income. She realizes that, if she is open about the items being counterfeits, she could probably get away with selling small amounts of the remaining stock that her father had brought with them and places an ad, specifying the fake nature of the items, in a local advertising circular. She gets a few responses, but dismisses most of them due to her fear of communicating with male strangers. One of the responses, though, seems to be from a young girl, whose sloppy handwriting and poor grammar point to her being no more than 13 or so. Because the girl lives nearby, Momoko invites her to come examine the goods. When she arrives, though, it turns out that she is a young woman of Momoko's age who is also a motorcycle-riding, hard-fighting Yanki (or biker-gang chick). In the first of many parallels between the girls, just as Momoko mistook Ichiko, the biker, for being a child due to her letter, so Ichiko mistakes Momoko for being younger than she is due to the frilly dress Momoko is wearing when they meet.
After this chance meeting, Ichiko continues to come over and visit, ostensibly to act as a go-between for the rest of her girl gang in buying counterfeit fashion items, which the Yankis go wild for, and the two girls spend more time together. Momoko isn't sure why, but she's never really understood the interactions of people well. Her only real connection in life has been with the Lolita dresses and accessories with which she surrounds herself. In a second parallel between the girls, we are shown how both Momoko and Ichiko externalize their developing sense of self, Momoko into clothing, Ichiko into her tricked out 50cc scooter. Another parallel drawn is between the girls' names. Each feels that they have been given a name that doesn't reflect their inner self: Momoko's name (which means "Peach Girl", and is related to one of Japan's greatest mythic/folklore heroes, Momotarō the Peach Boy) was used for a character in a famous biker manga, and so everyone expects her to be a tough, hard-riding, gangster chick. Meanwhile, it turns out that Ichiko is really Ichigo "Strawberry" (and her family name, Shiroyuri, means "white lily"), which is all Momoko will call her after she learns the truth.
After a while of getting to know each other, Ichigo learns that Momoko buys her clothing in Tokyo, and asks if she knows of a legendary embroiderer called "Emma". Ichigo wants to have her biker coat embroidered with a tribute to her biker gang leader, Akimi, the woman who treated her well when she had run away from home once. Akimi is planning to retire from the gang soon, and they are planning to have a special "parade", where the bikers ride around the town as a way of celebrating. Momoko doesn't know the embroiderer, and suspects that the business doesn't exist, but agrees to look for it. In the course of this conversation, Ichigo also explains about another legendary figure among girl bikers (as Momoko notes, the bikers seem to be surrounded by "legendary" figures), Himiko, who purged the gangs of exploitive criminal elements such as drugs and prostitution, but who vanished after demolishing the local yakuza.
Ichigo convinces Momoko to come play pachinko as a way to make money, in part to pay for the embroidery. Momoko grudgingly agrees to come watch, but when she gets bored watching Ichigo lose, she puts a few yen into a machine she chooses because it is cute and accidentally learns that she has a natural talent for the game, winning big. For a few weeks, the two go around pachinko parlors, Momoko winning enough that the parlor operators start to suspect that the two are cheating. At this point, they meet an up-and-coming yakuza tough who gives them advice on how not to be suspected. Ichigo notes that he happens to have the same design of a god riding a tiger (Momoko points out in her narrative that this particular god normally rides a cloud, not a tiger, and finds the whole thing terribly vulgar) on the back of his jacket as Akimi has on the front of hers, and takes that as an omen. Furthermore, Ichigo is smitten by the young man, but is too afraid to do anything about it.
After searching for Emma's online, Momoko runs into nothing but dead ends, so they decide to go to Tokyo to search the streets (and, not incidentally, to visit Momoko's favorite boutique, Baby, the Stars Shine Bright). Momoko notices that the back of Ichigo's jacket is strange, and asks what it is supposed to mean. Ichigo responds that it is go-iken-muyo "no use for your opinion", but Momoko informs her that the last character is actually buzama "shabby", making it a weird way to say "shabby opinion".
When they arrive at Baby, the Stars Shine Bright, the saleswoman notices that Momoko has added embroidery to the bonnet she'd bought from there. Momoko explains that she had to repair it after moths or mice had chewed it. The saleswoman calls the bonnet to the attention of a man who Momoko first takes for a delivery boy, but then realizes is actually Akinori Isobe, the chief designer for Baby, the Stars Shine Bright. She finds herself tongue-tied because he is the man who defined her life, as it were, through his fashion designs. He looks appreciatively at her embroidery work and gives her some free merchandise, but leaves after a polite farewell (a somewhat different scene than portrayed in the film).
Energized by this encounter, Momoko resumes the search for "Emma", and finds it when she remembers to check a phone book instead of just online. Hurrying there, the girls find out that it is the address of an embroidery teacher, not an embroiderer, but the teacher notes that there was once an embroiderer by that name who worked on biker regalia in a different area, but he died 15 years ago. She figures that the similarity of names caused bikers to think that he had moved, since she has had to inform a large number of them who show up on occasion looking for the legendary embroiderer.
Disappointed, Ichigo gives up on the idea of embroidering her coat, but Momoko offers to do it instead. There follows a detailed description of her search for the right font and stitching to use. She then loses herself in the work, stitching without break from the evening of Monday through the morning of Wednesday. Because she is Momoko, she adds a small strawberry to the work (which you can see if you look carefully in the movie). When she presents the coat to Ichigo, the biker is not entirely pleased by the addition of the berry, but is so impressed by the amazing (one might even say legendary) quality that she decides to overlook it. She says, "I didn't even know embroidery could be this beautiful."
The day after the parade, Ichigo calls Momoko and asks her to meet her by the river. There, she tells Momoko all about it, and then reveals that Akimi's reason for retiring was that she was engaged to the young yakuza tough that Ichigo had fallen for, and that she was pregnant with his child. Momoko refuses to offer platitudes and just stands by with a handkerchief while Ichigo cries the pain of unrequited love away.
A few days later, Momoko gets an email from Akinori Isobe of Baby, the Stars Shine Bright, asking her to please contact him about an urgent matter and giving a phone number. When she does, he tells her that he needs her to do some embroidery work for him, as the factory has made a mistake and shipped some of the samples without the designs. He needs them for a photo shoot that is happening soon. She agrees, and spends three days finishing the work, in plenty of time. Ichigo comes with her to present the finished items to Isobe. He recognizes Momoko's work on the front of Ichigo's coat right away, and is duly impressed with her work on his jumpers.
Unfortunately, the model who was to wear the clothes in the photo shoot is injured, accidentally, by her manager (he gives her wart remover instead of eye drops, forcing her to go to the hospital). Looking around, Isobe notices Ichigo and asks her to be the model for the shoot. Ichigo has a natural talent for modeling, and after the photo spread is published gets offers for more work, which she takes on, but only when it doesn't interfere with her biker activities, work, school, or anything else in her life. The ad also generates a lot of demand for the jumper with Momoko's embroidery, and Isobe asks if she'd be willing to take on a limited-edition line of them (say, 30 jumpers).
Meanwhile, Ichigo's biker gang starts to change, become more "political", as the new leader, Miko, wants to unify with other local girl-gangs and become bigger. Ichigo isn't thrilled with this, nor with the increased discipline under Anna, their fight squad leader. Because of her attitude toward the new order and her work modeling, Ichigo says that she is being asked to "draw the line", but doesn't explain what that means. Momoko asks The Loser, and he informs her that, in the yakuza, it would be having your pinky finger chopped, and in biker gangs it varied, but could range from being burned by lit cigarettes to being dragged behind a motorcycle at speed. Momoko borrows her grandmother's Viva You scooter (a collaboration from back in the '80s between Honda and the Viva You fashion brand, like if it were a Swatch scooter) and races to be by her friend's side at the Ushika Buddha, a giant statue of the Buddha.
She finds Ichigo surrounded by around 30 biker girls armed with chains, bats, and the like. She hits the brakes too hard and the scooter spills her, the engine cracking and smoking. Ichigo explains that she is going to go it alone, like Momoko, not following orders or obeying rules, and accuses the bikers of being sheep. Miko claims that she and the leader of another gang were told by Himiko, the legendary biker, to unify the gangs, and that Ichigo is stabbing them in the back by trying to leave. For those who have seen the film, the fight plays out quite differently, with the balloons of water that Momoko's father was making being of some importance. There's also no speech about being Himiko and Emma's daughter.
After the fight, as they are riding away, Ichigo tells Momoko about how she had accidentally invented Himiko. She offers to have her mechanic friend pick up the damaged Viva You scooter. As they ride away, Momoko thinks about how, if Baby, the Stars Shine Bright were to make a scooter like Viva You did, she'd be happy to get a license to ride it, then lays her head against Ichigo's back "the way I might with a lover".