Akihito Hayasaka, a second-year student at St. Francesca Academy, navigates the social complexities of a recently co-ed school still dominated by female peers after transferring from the defunct Takamiya Academy. Haunted by the childhood loss of his biological sister in a fatal accident, he withdrew emotionally until his adoptive sister Umi, a spirited first-year at the same academy, helped him rebuild fractured connections. Their bond anchors him as he interacts with childhood friend Yuika Serizawa, whose buoyant personality contrasts his once-reclusive nature, and navigates clashes with strong-willed classmate Riru Orito and composed student council president Kisaya Fuyurugi.

Assigned to the male-minority "Soleil" class, Akihito becomes an inadvertent focal point in the academy’s evolving dynamics, his relationships blending romantic tension, comedic friction, and incremental personal growth. The shadow of his sister’s death and his status as a transfer student inform his cautious yet evolving engagement with newfound social circles. Expanded narratives, including original video animations, delve deeper into his unresolved conflicts and tentative romantic entanglements, underscoring his journey from trauma-induced isolation to hesitant emotional vulnerability across multiple storytelling mediums.