Based on the erotic game by Cattleya.

Yohei happily lives with his mother, Kaho, and his cousin, Fumika. But one day, Kaho tells Yohei that Kaho is actually an older sister of his father, not his mother.... She also tells him that his mother passed away long time ago. Yohei is shocked to hear that, but he starts seeing Kaho as a woman, n...