Ten years have passed since Yuu divorced, and now her son Ryo is destined to meet his new stepfather. For Ryo, who has few memories of his biological father, the formation of a new family brings both joy and feelings of embarrassment and anxiety. Naturally, he also feels loneliness, fearing he might lose the mother he loves so much. Today is the day he meets his mother's new husband for the first time. The man introduced by Yuu turns out to be someone Ryo has known since childhood—his closest friend. This revelation brings an unbearable shock, one that Ryo is completely unprepared to face.