Yosuke's older sister, Tamaki, has always been provocative with her sexy outfits. When Kazuya goes to visit Yosuke for the first time in a while, he accidentally witnesses the brother and sister cleaning up after sex in Yosuke's room. Kazuya is surprised. Tamaki, who has now discovered her relationship with her brother, starts masturbating in the room, knowing that Kazuya is watching her. Kazuya is in a state of agony as he is forced to watch his sister like that, and soaks in the bath. Then Tamaki, the person involved, finally appears. Kazuya is on the verge of exploding!?