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作品概要
Yuuka has recently started going out with Kouta, the childhood friend she's always had a crush on. Two months into their relationship, they go to Kouta's house to have sex for the first time, but because both of them are inexperienced, it doesn't go well. In front of a troubled Yuuka appears Kouta's younger sister. "Become my ideal girl." A boyfriend, a girlfriend, and his younger sister. It's the start of a love triangle that's so sensual you can't look away, but so immoral that you'll wish you could. (Source: Kodansha, translated)
來源: AniList
劇情簡介 日本語
晃汰と優菓幼馴染だった二人は恋人になってある日、晃汰の家で初体験を迎えたが上手くできなかった。悩む優菓に晃汰の妹雛乃が現れて自分の理想の女の子になるように要求する。
來源: Wikipedia「あなたの妹」 (CC BY-SA 4.0)
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