From Deux:
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.

Note about the volume number:
It looks like there might be two versions of series (about 2 volumes each) rather than 4 continuous volumes. The American companies that have published this series, Deux and Sublime, have published the two volumes of the pink version (愛人☆淫魔 ｖｅｒ．ＰＩＮＫ). This is why they claim the have finished the series even though there are two others left unpublished.