One Loves Monster

Yume Sonozaki is a shy, reserved college girl who's inexperienced with love. At her after-school club, she hits it off with a nice older student, Aoi, who becomes her first boyfriend. She's happy with him, but for some reason, they haven't gotten to first base! As the days go by, she finds herself sadder and more desperate. Yume finally bites the bullet and asks if she can stay the night, and a bewildered Aoi agrees. Nervously, she waits for Aoi to step out of the shower, only to discover his personality has changed completely. What is this strange, animalistic allure? Thus begins a love triangle with two men in the same body!

(Source: Renta!)