After a marital dispute angered his wife, Kazuya found himself in distress when she stormed off to her parents' house. With no solution in sight, he was left completely baffled. Seeing his struggle, his wife's older sister, Shoko, offered to listen to his problems. Beautiful, kind, and nurturing, Shoko's warmth gradually made Kazuya let down his guard. However, Shoko's true intention wasn't to mend their marriage—but to use Kazuya to satisfy her own pent-up desires.