Your Sister

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 s** 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.