Uchi no Koakuma-kun

A succubus is a beautiful being that seduces human males to consume their energy. They are the super idols of the devildom. Spica, a little demon who yearns to become a succubus, breaks the law to travel to the human world alone. There, he finds a human male to attack. He tries to steal his energy by having sex, but the human thinks the whole situation... is just a dream?!

(Source: Ichijinsha, translated)