This is the story of Rena, a magical girl who has been transformed into a futanari, discovering the pleasures of a penis and falling into depravity.
Rena is the strongest magical girl who protects the peace of the city. However, due to a moment of carelessness, she is put under a spell by a mysterious person and loses consciousness. When she wakes up, her hands are locked and she is completely restrained. And... between her legs, a "thing" that shouldn't have been there has grown... And then the mysterious person from before appears. With her help, Rena experiences all kinds of pleasure with her body and her huge erect penis! Why did was the futanari spell casted on Rena? What choice will Rena make after learning the truth...?