Kyoko became Shingo's older sister after their parents remarried. While their parents are overseas, she lives alone with Shingo. She hides her sexual desire in front of her brother, but she's actually a super slut who desperately wants to get pregnant. As they live together, her lust for Shingo grows stronger. She makes him drink an aphrodisiac and plans to have sex with him. She even makes Shingo's friend drink it and seduces both of them...