My Friend's Abnormally Cute SisterOsananajimi no Ijou Kawaii Imouto-chan; 幼馴染の異常可愛い妹ちゃん; My Friend's Abnormally Cute Sister; 发小的异常可爱的妹妹; 发小的巨可爱妹妹; 發小的異常可愛的妹妹; 發小的巨可愛妹妹; Cô Em Gái Dễ Thương Nhưng Lạ Thường Của Bạn Tôi

Yanagi, a second-year high school student, has a faint crush on Mizuki, the younger sister of her childhood friend Momo. One day, while rummaging through Mizuki's personal belongings in her room, Yanagi discovers the truth about Mizuki...?