Entering a stage of life between childhood and adulthood, 12‑year‑old Hanabi Ayase and Aoi Yui encounter events that change everything. Because of her classmates" playful behavior, Ayase holds a low opinion of boys. Yet her view shifts when she partners with the gentle Takao Yuuto for a school project and they unexpectedly share their first kiss atop the campus roof. Meanwhile, Aoi watches her best friend fall in love and longs to find romance herself. She becomes attracted to the impulsive Kazuma Hiyama after shielding her from a disapproved admirer who had spoken ill behind her back. The series 12‑Sai: Chicchana Mune no Tokimeki follows these four during adolescence, portraying the innocence and thrill of first love as they grow together in a world that feels both strange and familiar, their hearts beating in sync other, discovering hope.
