Kaga Ryosuke is an ecchi high school boy. One day, he meets a girl standing alone in the rain. She is Lisarah Restor, an elite Death, who visited the human world in order to find "Singular Man".
Ryosuke makes a contract with Lisarah and she sucks energy required for her activity in the human world from Ryosuke. The source of the energy is his ecchi spirit.
To recover the sexual desire, Ryosuke has no choice but to help Lisarah's search.