Kazuya's elder sister Kanoko announces her engagement to be married but Kazuya has had a crush on her since he was young and refuses to let her go. He wants to become her lover and be her only man but she refuses because that would be incestuous. She encourages him to build a relationship with his cousin Hikari instead but he won't give up his feelings for his sister.

Meanwhile Hikari's father and Kazuya's uncle is dying and both Hikari and Kazuya's aunt Chigusa cling to him in desperation for comfort.