So, I Can't Play H (2012)

High schooler Ryosuke Kaga is also known as Erosuke for his extreme adolescent interest in the erotic side of life. One day he encounters a young girl standing alone in the rain. She is Lisara Restor, an elite Death God who has come to Earth in search of a human known as the "Singular Man." Ryosuke ends up making a contract with Lisara, allowing her to suck the energy she needs for her activities on Earth from him. And it turns out the source of that energy is his own perverted spirit. As a result Ryosuke can no longer feel aroused in the heat of the moment. After trying every erotic method he can think of, he finds he has no choice but to help Lisara in her search in order to recover his perverted spirit."