Hallelujah and The Succubus!

A veterinary student, Hallelujah Tendo is an honest person whom everybody calls "the angel of the veterinary faculty." One day, he helps a mysterious creature with bat-like wings, but it turns out to be the super cranky demon, Lucif! Lucif has been purged from the heaven by the angel Micha, with the succubus seed implanted inside his body. Touched by Hallelujah, he is instantly turned on and from the extreme hunger, orders Hallelujah to "Put your semen...inside of me now." Unable to grasp the situation, Hallelujah is robbed his virginity and even worse, he is tied with Lucif by magical collars and chains. His new life begins and he must frequently provide Lucif with his semen... As Lucif gradually recovers his power, his fellow demon, Baal Belial senses his presence and appears at Hallelujah's place to bring him back to the Hell.

(Source: MangaPlaza)