The story begins with the protagonist, Itsuki Ebina, being summoned to the school rooftop by his childhood friend and girlfriend, Karen Negishi. To his surprise, Karen breaks up with him, citing his alleged wrongdoing as the reason. Itsuki is devastated, as he has been ostracized by the entire school for three months due to a misunderstanding or false accusation, and Karen was the only one he hoped would believe him. Karen reveals she is now dating Sunaoka-senpai and leaves Itsuki heartbroken, especially as he recalls their shared past and promises. His despair is amplified when his classmates, who had been waiting, mock him and record his humiliation to spread online.
Feeling utterly alone, Itsuki, who is secretly a popular web novelist known as "Shiiku-gari," impulsively tweets about his breakup. He then encounters a younger student, Hinata Atsugi, being harassed by delinquents. Despite his own troubles and the expectation of further scorn, Itsuki intervenes. He pretends to be Hinata's boyfriend to ward off the attackers, but they retaliate, leaving him beaten. Adults arrive, scaring off the delinquents. Hinata expresses gratitude and insists on calling Itsuki by his first name, hinting at a budding, perhaps overly familiar, relationship.
A week later, Hinata begins to persistently visit Itsuki at the abandoned calligraphy club room, where he seeks solitude. She declares him her future husband, much to his apprehension, as he fears she will eventually reject him like Karen. However, Hinata reveals she believes in his innocence, having observed his quiet acts of kindness, such as fixing bicycles and participating in volunteer cleanups. This unwavering faith brings Itsuki immense relief and joy, and they spend hours talking, a rare comfort for him.
Meanwhile, Karen reflects on her breakup with Itsuki, justifying her actions to Sunaoka-senpai, who consoles her. She claims to have forgotten Itsuki and embraces her new relationship with Sunaoka. However, upon seeing Itsuki's tweet about his breakup, a pang of guilt surfaces. She then discovers that Itsuki is the popular author "Shiiku-gari" and realizes that many of his published stories mirror their shared childhood memories and their relationship, leading her to question her decision and feel a growing sense of regret.
Itsuki's life takes another turn when Hinata, who has been visiting him, reveals she has a key to his apartment and has cooked him dinner. She then probes into his family life, prompting Itsuki to share his painful past: his strained relationship with his parents who favored his talented older brother, and his subsequent decision to live alone. Hinata, in turn, confides in him about her own feelings of being an unwanted child in her family, leading to a deeper connection between them.
The next day at school, Itsuki is subjected to bullying, but Hinata intervenes, defending him fiercely. When the bullies bring up a past accusation of assault against Itsuki, a classmate named Hiyoshi, who was supposedly the victim, feigns distress. Hinata, however, challenges their narrative, pointing out the lack of evidence and Hiyoshi's inconsistent behavior. Itsuki, worried about Hinata becoming a target, tries to de-escalate the situation, but Hinata, using a recording of the bullies' taunts, silences them.
Later, Itsuki's classmate Yamato, a fellow loner, approaches him to apologize and express his belief in Itsuki's innocence, citing his love for mystery novels. Yamato, mistaking Hinata for a life-sized figure, eventually accepts she is Itsuki's "sister" and offers his friendship, creating a tentative social circle for Itsuki.
The narrative then shifts to Karen, who observes Itsuki and Hinata together, feeling a mix of disdain and jealousy. She continues to follow "Shiiku-gari" online and notices the author's tweets mirroring Itsuki's recent interactions with Hinata. This, combined with her reading of "Shiiku-gari's" web novels, which contain many of their shared memories, leads her to suspect Itsuki is the author. She contrasts Itsuki's perceived "loser" image with the successful author and her current boyfriend, Sunaoka, but her past memories and the author's writings begin to stir a deep sense of regret.
In the abandoned calligraphy club room, Itsuki and Hinata are interrupted by the arrival of Riko, a girl who identifies herself as Hinata's "maid" and fiercely protective of her. Riko initially confronts Itsuki, suspecting him of having ill intentions towards Hinata, but after Itsuki vehemently defends Hinata, Riko grudgingly accepts him as a rival, albeit a potentially dangerous one. The chapter ends with another knock on the door.
