The story begins with Kujo Saitou, a 16-year-old high school student, on his usual morning commute. He is abruptly drawn into a confrontation on the train when a man in construction attire aggressively provokes a stylishly dressed male student. Saitou, despite his initial reluctance to get involved, intervenes to de-escalate the situation. The aggressor, who Saitou assesses as young and likely inexperienced, turns his attention to Saitou, demanding he leave the train at the next station for a private confrontation. Saitou agrees, as the next station is his school's stop.
After exiting the train, Saitou calls for help from a station attendant, successfully drawing attention to the aggressor's actions. The aggressor is apprehended by station staff, and Saitou is questioned by the police. He truthfully recounts his role as a mediator, but the police, due to his age and the nature of the incident, initially suspect him of more serious offenses like molestation or voyeurism. His class teacher, Neya Tsuyoshi, who is also Saitou's cousin and guardian, intervenes to clarify the situation and prevent the school administration from escalating the misunderstanding.
Later, Saitou's friend, Nishino Rinna, a beautiful but sharp-tongued girl, expresses concern and reveals that a video of the train incident has gone viral online, with Saitou being dubbed "Maamaa-niki" for his repeated use of the phrase "Maamaa" (meaning "calm down"). This newfound internet fame leads to unexpected attention at school, with classmates, including girls from other classes and a quiet student named Nakajo Ako, approaching him. The victim of the initial assault, Hoshina Rei, a handsome and seemingly well-off high school student, also contacts Saitou.
Rei's mother, Hoshina Suzuon, a famous actress known as Hoshina Kanon, invites Saitou to her luxurious tower apartment to discuss the online fallout and legal proceedings against the video uploader. During his visit, Saitou and Rei bond over video games, and Saitou learns about Rei's sheltered upbringing and his mother's protective nature. Rei's mother, Suzuon, takes charge of pursuing legal action against the person who uploaded the video, enlisting her lawyer to handle the matter.
The narrative then shifts to Saitou's daily life, where he continues to navigate his unexpected internet fame and his growing friendship with Rei. Rei, still recovering from his injuries and taking time off school, becomes increasingly attached to Saitou, expressing jealousy when Saitou mentions his female friend Rinna. Saitou, meanwhile, finds himself caught between his desire to maintain a normal life and the escalating attention stemming from the online video and his involvement in the incident. The chapters conclude with Saitou receiving numerous messages from Rei, indicating a potentially complicated development in their relationship.
