Three years after leaving home, Yuu's long student life is finally over. His parents are absent from the graduation ceremony, leaving him to make the lonely trip back alone—until his stepmother Yumi appears with a smile. Yuu has secretly desired her as a woman and cannot hide his delight. During their private celebration, Yumi drinks too much, and he helps her to an inn. There, the stepmother he has always wanted gives her adult stepson an intimate graduation gift.