The third exclusive release! Ikumi Kiho's first drama! The electricity and gas were cut off at my house, so I ended up staying at my girlfriend's house. She has a younger sister, and this is the first time we've met... but she seems wary of me. That night, after she refused to have sex with me, I was masturbating when her younger sister saw me! She seems to be weak to pressure, so maybe I could do it... I spent a week secretly fucking with my younger sister without my girlfriend knowing. Gradually, her temptations escalated...