Yosuke is Haruka's boyfriend and the two are living together. Yosuke and Haruka work different hours, so they have very little time together. Yosuke begged Haruka for permission to have sex together today because it had been a long time since they had done it. Haruka agreed to let Yosuke do it as he pleases when he comes home from work. After coming home from work, she saw her lover sleeping, today she wore an extremely charming pair of underwear that Yosuke couldn't hold back anymore. As he was acting, he saw the face of the girl below, it was Kanon-chan, his girlfriend's sister! So today she quarreled with her mother, so she came here to hide. But fortunately, she didn't stay long, and when Yosuke came home from work tomorrow morning, she was already home. And Haruka promised to compensate him for today's incident. When I got home, I saw a naked woman, wrapped in a towel, coming out of the bathroom. Thinking that his girlfriend because Kanon had to come home now, Yosuke didn't hesitate anymore. He quickly rushed at her, releasing all the discomfort he had been uncomfortable for many days. But while he was happy, the towel slipped off, and the girl he was having sex with was Kanon! Because of panic and confusion, he lost control and put all his semen inside his lover's sister...