Naoto Watari has raised his younger sister Suzushiro alone since their parents died, earning a reputation at school as obsessively overprotective. His careful, closed-off routine breaks down when childhood friend Satsuki Tachibana reenters his life. She is the same Satsuki whose past actions once wrecked his family's garden. As she starts making pointed overtures toward him, old wounds resurface and new complications threaten the household he's spent years holding together.