Succubus Stayed Life

The story follows Haruyuki Matsukawa, a high school student living alone after his parents leave for work. One day, his quiet classmate Touko Sakuramachi suddenly confesses that she is actually a succubus who survives by draining sexual energy from humans. Matsukawa initially assumes it's a joke, but he quickly discovers she was serious when she moves in with him to use him as a steady energy source.