Yuina, a girl in love with her non-biological brother, lives tormented by her lack of self-confidence. One day, she is guided to an unknown world by a mysterious voice. Without understanding what is happening, she is attacked by a man. In that desperate moment, she is saved by the specter of a succubus that possesses her body. The succubus defeats all enemies by fucking them, regardless of what happens to Yuinas body and mind.