Aijin Incubus summary:

Fujimaru is your average adolescent boy - horny and girl-crazed. Like many boys his age, he enjoys spending ‘alone time’ in the bathroom with erotic magazines, doing… you know. Unlike many boys his age, Fujimaru has a demon incubus, Rei, lurking about his house. Rei wants nothing more than to feed off of Fujimaru’s perverted mind! Now Fujimaru’s life has become strained with being a normal boy whose raging hormones are the source of a demonic incubus’s food.