幼馴染の裕美と付き合い彼女の家に遊びに行った健太。裕美の妹・和花に10年ぶりに会ったら低いテンションで健太に憎まれ口を叩いている…。しかし和花は、裕美の目を盗み誘惑してくる！？不覚にもチンイラして誘惑に負けてしまう健太。裕美の目を盗み何度もダウナー系痴女の和花とセックスをしてしまう。容赦ない誘惑に理性はぶっ壊れ・中出ししても止まらない…

Kenta, who is dating his hood friend Yumi, visits her house. He meets Yumi's younger sister, Waka, for the first time in 10 years, only to find her in a low mood and spiteful remarks towards him… But when Yumi isn't looking, Waka starts to seduce him! To his dismay, Kenta gets aroused and succumbs to her temptation. He repeatedly has sex with the gloomy, slutty Waka while Yumi isn't looking. His reason is shattered by her relentless temptation, and he can't stop even after ejaculating inside her…