彼女が僕の家に遊びに来た際に一緒にやってきた妹の夕莉ちゃんは、授業で習った「性行為」に興味津々。そんな夕莉ちゃんですが胸だけは発育が凄く大人でも驚くほどの大きさ。ただ自分の身体の魅力には鈍感で「性行為」を経験したいが為におっぱいを使って僕を無邪気に誘惑してきます…。やがて一線を超えてしまってからは定期的に僕の家に遊びに来ては’気持ち良いSEXという行為’をせがまれるようになってしまいました…。
When she came to my house to play, my younger sister, Yuri, who came with me, was very interested in the “sex act” that I learned in class. Yuuri is like that, but only her breasts are so big that even adults are surprised by their growth. She’s just insensitive to the charm of her own body and wants to experience “sex”, but she innocently seduces me with her breasts… Eventually, after crossing the line, he came to visit my house regularly and was pestered for ‘the act of pleasant sex’.

– JavGG.net