In Eastern Europe, there is a certain hotel renovated from an old castle. Traveling from Japan, at this place, the protagonist successfully proposes to his girlfriend. However, due to her work, she returns to her home country first...... The protagonist, now alone, has a strange dream. Turned into a girl, the dream takes him to the old castle when it was still prosperous. There, he meets a twin boy and girl, calling themselves the Devil​, the dream lets him taste the pleasure while being in a girl's body. After waking up from the dream, he finds himself turned into the same girl he was in his dream. He tries to do something about it, but every time he falls asleep, he experiences the same dream. ――In this old castle, while being a girl, he is drowning in pleasures. And when he wakes up, his body is becoming more and more feminized. In this situation, even though he manages to propose, he cannot reunite with his lover. While getting flustered, the taste of pleasure while being a girl, more than in a man's body, it becomes sweeter and irresistible...... Will the protagonist be able to escape from the dream and go back to being a man? Or..... [Translated and edited from the official website]