Haru Yoshida, a high school student suspended for violent behavior, becomes socially isolated and feared as the school’s “monster.” His academic brilliance lets him master material independently, earning top exam rankings effortlessly, sparking rivalry with Shizuku Mizutani—a classmate assigned to deliver his missed assignments. Their encounters reignite his return to school and an obsessive emotional attachment, marked by impulsive love declarations and jealousy-fueled possessiveness, particularly toward her interactions with peers like Kenji Yamaguchi. Raised in a fractured family, Haru endures a childhood shaped by parental divorce and estrangement from his father. After the separation, he moves to the countryside with older brother Yūzan and caretaker Tone, forming a deep bond with Yūzan. Familial pressures and academic demands fuel Yūzan’s resentment, culminating in Haru’s expulsion from the Yoshida household due to behavioral issues and falling grades. He relocates to his paternal aunt Kyoko Misawa, whose lessons on love and human connection leave a lasting impact. Following her death, he joins cousin Mitsuyoshi Misawa, who offers steadfast brotherly support. Struggling with past trauma and possible neurodivergent traits, Haru battles social cues and emotional regulation, often reacting with violence or impulsivity. Middle school bullying by Kenji, countered by Yūzan’s protection, deepens his distrust of others. Yet he displays innocence and a yearning to connect, seen in his devotion to pet chicken Nagoya and attempts to mimic social behaviors like smiling for acceptance. His dynamic with Shizuku shifts from one-sided infatuation to mutual growth. Early boundary-crossing actions—like threats to silence her—give way to self-awareness, leading him to respect her space and academic ambitions. When Shizuku confesses her feelings, Haru confronts abandonment fears. After a year-long tuna-fishing hiatus, they reconcile, marrying post-graduation. Friendships with classmates like Asako Natsume and Sōhei Sasahara reveal his loyalty and protective instincts. He tutors Asako despite initial friction, forging bonds through mutual aid. His rivalry-turned-camaraderie with Kenji, who becomes his best man, highlights his capacity for forgiveness. Family ties remain strained, particularly with Yūzan, whose reconciliation efforts Haru resists over past betrayals. Across manga, anime, and film adaptations, Haru’s journey centers on overcoming isolation through empathy. Notable moments include constructing a chicken coop for Nagoya with classmates—a testament to his commitment to nurturing bonds—and confronting Yūzan during a school festival clash, forcing him to address unresolved family strife. His eventual maturity blends emotional stability with measured consideration for others, tempering his once-unchecked impulsivity.