Chizuru Tachibana, a half-Japanese, half-German transfer student, joins the established friend group at Homare High School. He stands 162.4 cm tall, a height that often causes him insecurity. His blonde hair, usually styled with wax, falls down when wet. A distinctive mole under his right eye is a feature he considers his "best." Born on August 11th with blood type O, he previously visited Japan years before transferring and briefly encountered Yūki and Yūta Asaba then, despite not knowing Japanese at the time. Now fluent, he returns for high school.

Cheerful, playful, and noisy, Chizuru's personality contrasts with his more reserved friends. He frequently engages in mischief with Yūki, often provoking Kaname Tsukahara's temper. He assigns nicknames to everyone, calling Masaki Satō "Mary" due to her sheep-like hair. Chizuru develops romantic feelings for Masaki, who remains oblivious as she harbors a crush on Shun Matsuoka. His affection shows through protective actions, like carrying her to the infirmary when injured, and self-sacrificing gestures. At Christmas, he replaces the damaged ribbon on her gift to Shun with his own, then watches her present it while crying alone in the rain. On Valentine’s Day, witnessing Masaki's distress over another girl's failed confession to Shun, he encourages her to confess. Immediately afterward, Chizuru confesses his own feelings to Masaki, expressing happiness in loving her despite the pain of unrequited affection. His confession surprises her, as she had only seen him as an annoying classmate.

Following his confession, interactions between Chizuru and Masaki become awkward, especially during graduation, though they eventually reconcile without immediate romantic resolution. Throughout, Chizuru continues to support Masaki emotionally while navigating his feelings. He likes playing, curry rice, snack foods, and staying up all night, but dislikes studying. His surname Tachibana (橘) means "orange/tangerine," and his given name Chizuru (千鶴) combines "thousand" (千) and "crane" (鶴), referencing the Japanese legend that folding a thousand origami cranes grants a wish.