An unnamed speaker describes pictures of a man later revealed to be Yozo. There are three pictures of him: one as a child, one when he’s slightly older, and one as an adult. The unnamed speaker finds each picture grotesque, saying he can hardly recognize Yozo as a human, even though he knows most people would find Yozo good-looking. But, the speaker says, there’s something deeply disturbing about Yozo, especially in the final picture, in which he stands in a run-down room while staring at the camera with a blank expression.
The novel then presents Yozo’s personal notebooks. He begins by describing his childhood, explaining that certain things about society and humanity never made much sense to him. He has never seen the point of eating big meals, for instance, but he always eats large amounts to please other people. As a young boy, he feels depressed by what he sees as “human dullness,” which is something he picks up on when he thinks about the logical, unaesthetic way people move through life. At one point, several members of his family’s waitstaff sexually abuse him, and he feels unable to tell anyone about it. The experience makes him feel “corrupted.”
Yozo feels unable or unwilling to let his “true nature” show, so he develops a technique of performing for the people in his life. He thinks of himself as a clown who’s willing to do anything to get others to laugh, and he becomes quite good at endearing himself to people. One day, though, he purposefully falls down at school, and while everyone is laughing, a quiet boy named Takeichi comes up behind him and whispers, “You did it on purpose.” Yozo is horrified to learn that Takeichi—whom he thought was unintelligent—can see right through his entire act. He decides to get as close as possible to Takeichi, hoping this will allow him to keep an eye on him. After some false starts, he manages to bring Takeichi back to his house during a rainstorm, and he gently dries his new friend, prompting Takeichi to say that women will surely go crazy for him later in life—a comment that ends up being true, though it unsettles Yozo.
One day, Takeichi shows Yozo a famous painting. Yozo recognizes it as Van Gogh’s self-portrait, but Takeichi says it’s a painting of a ghost. The comment astounds Yozo, prompting him to reconsider the way he looks at art. Many paintings, he realizes, aren’t beautiful portraits meant to be passively admired—they’re visceral depictions of life’s horror. He decides to become an artist himself and starts creating disturbing paintings that convey his “true nature,” which he otherwise keeps hidden. He only shows the paintings to Takeichi.
Years later, Yozo goes to college in Tokyo and studies art while living in a townhouse that his father owns. His father is a politician, so he uses the townhouse when he’s in Tokyo for legislative sessions. For the most part, Yozo hardly sees his father, instead spending his time with a classmate named Horiki, who shows him how to lead the rough-and-tumble life of a young artist. He introduces Yozo to drinking, smoking, and sleeping with sex workers. Despite their new friendship, though, Yozo doesn’t actually like Horiki, even if he appreciates having a drinking companion. Horiki also brings him to a Communist Party meeting. Although Yozo finds the people there ridiculous for thinking their Marxist beliefs actually matter, he pretends to feel the same way and eventually becomes widely popular amongst his new “comrades.”
Yozo spends all of his time drinking, smoking, and running errands for the Communist Party. He hardly attends class. Soon, though, his father decides to sell the townhouse. Until this point, Yozo has been living on a small monthly allowance, but he tends to use that up within the first few days of every month. He usually manages to buy what he needs by putting things on his father’s tab at the local stores, but that’s no longer possible. He suddenly feels what it’s like to experience poverty, but this doesn’t keep him from drinking. He becomes deeply depressed. He still fears other human beings, and all he ever wants to do is get so drunk that he can’t feel anything. One night, Yozo goes to a bar and bluntly tells the bartender that he doesn’t have much money. But she doesn’t mind—she lets him drink on the house, joining him in his glum mood. Her name is Tsuneko, and she brings him back to her apartment later that night.
Tsuneko talks to Yozo all night about how unhappy she is. Listening to her makes him feel better, as if they’re connected through their suffering. The next time they spend the night together, Tsuneko says she can’t stand the idea of continuing to live, so they decide to die together by suicide. They throw themselves into the ocean, but Yozo survives. Tsuneko dies.
Yozo is taken to the hospital. Upon waking up, he’s arrested and charged with being an “accomplice to a suicide.” He spends the night in jail, but because he’s still recovering from the incident and has a nasty cough, the authorities aren’t as harsh on him as they could be. He’s released the next day and put under the supervision of an old family friend known as Flatfish. Yozo’s father, refuses to speak to Yozo, though his older brothers send Flatfish money. Yozo has also been expelled from the university, so he spends his days doing very little at Flatfish’s house. One evening, Flatfish calls him to dinner and asks what he wants to do with his life. He tells Yozo that he'll be happy to help him, as long as Yozo comes up with some sort of plan. Yozo can tell that Flatfish wants to hear him say something very specific, but he can’t fathom what this might be. Flatfish gets angry that Yozo’s life has no direction, prompting Yozo to finally say he wants to be a painter—something that makes Flatfish laugh.
The next morning, Yozo runs away from Flatfish’s house. He leaves a note with Horiki’s address on it, but he doesn’t intend to go to Horiki’s house. And yet, once he’s out wandering the streets, he realizes he has nowhere else to go, so he actually does go to Horiki’s. Like everyone else, Horiki has heard about what happened with Tsuneko, so he greets Yozo coldly. He clearly doesn’t want him there, but he still lets him in. Eventually, a woman named Shizuko stops by to collect an illustration that Horiki has made for a magazine she works for. Yozo ends up going home with her, and she seems happy to care for him, as if she’s attracted to his sadness.
Yozo lives at Shizuko’s house, along with her daughter, Shigeko. Shizuko’s husband died several years ago, and now she’s content to provide for Yozo. But Yozo soon grows restless, so he starts doing illustrations and cartoons for the magazine Shizuko works for, using the money to buy alcohol and cigarettes. He descends even deeper into depression, at which point Shizuko meets with Horiki and Flatfish. As a group, they decide that Yozo should marry Shizuko and have no more contact with his family. However, when Shigeko makes a comment about wanting her “real” father back, Yozo decides to leave.
Yozo goes to a bar in the Kyobashi neighborhood, and the bartender lets him drink for free and stay in an upstairs apartment. During this period, he continues to drink heavily until he meets a 17-year-old woman named Yoshiko. One night, Yozo is drunk and starts thinking about how Yoshiko must be a virgin, and he suggests that they get married—wanting, it seems, to experience what it’s like to have sex with a virgin. Yoshiko agrees to marry Yozo on the condition that he stop drinking. Yozo accepts Yoshiko’s condition but breaks his promise the following day. Nonetheless, Yoshiko is extremely trusting, so she doesn’t believe he would break his promise. They end up having sex and, shortly thereafter, marrying.
Yozo and Yoshiko move into a new apartment. For a while, life is good. Yozo stops drinking and begins to wonder if he might have a chance at happiness. But then Horiki reappears in his life. Yozo starts drinking again. One night, Yozo and Horiki hang out on the roof of Yozo’s apartment. They’re extremely drunk. At one point, Horiki goes downstairs to get some food, but he quickly returns and orders Yozo to come see what’s happening. When Yozo follows, he sees a man raping Yoshiko in an adjacent room. He’s horrified by what he sees, but he doesn’t interfere. Later, Yoshiko says the man assured her nothing would happen, and Yozo thinks about how Yoshiko is too trusting.
Yozo starts drinking even more. Upon coming home drunk one night, he finds a box of sleeping pills and takes them all, hoping they’ll kill him. He wakes up three days later, at which point Flatfish gives him some money to go recover at some hot springs. Yozo goes, but he spends the entire trip drinking. By the time he returns to Tokyo, he’s in a worse condition than before, frequently coughing blood and stumbling home drunk. He goes to a pharmacy to get medicine for his condition, and he instantly feels a strange connection with the elderly pharmacist. He can tell she’s another unhappy soul, and she seems to recognize the same thing in him. She tells him to stop drinking, giving him morphine instead. It isn’t long before Yozo is fully addicted to the morphine and constantly hectoring the pharmacist for higher doses. He starts having an affair with her to get more of the drug.
Once again, Yozo decides to kill himself. Before he can do so, though, Horiki and Flatfish take him to a psychiatric ward, where he feels like a “reject” and thinks he has been “disqualified as a human being.” Upon his release, one of his brothers sends him to the countryside, where he lives with an older maid who watches over him. His notebooks end with him saying that he has been in the countryside for three years and that, even though he’s only 27, he now looks like a much older man.
The novel’s final section returns to the unnamed speaker, who explains that the bartender from Kyobashi gave him Yozo’s notebooks, which Yozo seems to have sent her 10 years ago. The speaker came across the bartender while traveling in the country, and she thought he might be able to turn the notebooks into a novel. Instead, the speaker has decided to simply present the notebooks as they are, without changing anything.
