Yuu Kusakabe, a male student in Erika Shinohara’s class, struggles with profound shyness and social isolation rooted in childhood bullying. Mocked in elementary school for his delicate features and pale complexion—taunted as a “ghost”—he adopts the habit of hiding behind his hair, a defense mechanism that persists into high school. His quiet presence renders him nearly invisible to peers until he tentatively approaches Erika, Marin Tachibana, and Aki Tezuka to collect math notebooks, marking his first deliberate step toward connection.

A brief middle-school romance with Nagai, which dissolved upon entering high school, and familial worries—particularly from his sister and mother—about his inability to form relationships deepen his self-doubt. These insecurities solidify his withdrawn nature, though Erika’s persistent kindness begins chipping away at his shell. When she intervenes during his struggle to pay for groceries, covering the cost, the act ignites a tentative friendship. Encouraged by Erika, he slowly reveals his face and practices small social gestures, like greeting classmates, inching toward self-assurance.

Growing feelings for Erika clash with her turbulent dynamic with Kyoya Sata, whom Yuu perceives as callous. On Valentine’s Day, he confides his family’s teasing about never receiving chocolates, prompting Erika to impulsively gift him one meant for Kyoya—a gesture that fuels rivalry. Later, after Erika’s emotional fallout with Kyoya, Yuu confesses his feelings at a restaurant. Though rejected due to her unresolved attachment, he responds with grace, urging Kyoya to treat her better. His kindness endures, sustaining support for Erika while fostering an uneasy rapport with Kyoya, whom he eventually calls a “friend.”

By graduation, Yuu delivers a speech—a stark contrast to his former timidity—symbolizing his growth. The manga reveals his romantic relationship with Ryoku Edano, a detail omitted in the anime. His arc traces a path from isolation to self-acceptance, shaped by resilience, Erika’s influence, and the quiet courage to confront past wounds.