You're Being Summoned, Azazel

A young woman named Rinko Sakuma takes a job at a detective agency, and her new boss turns out to be quite peculiar: Akutabe is a dark sorcerer who summons demons to deal with his clients' troubles. He has his new assistant sign a contract with Azazel, a small demon of extremely lecherous nature. Akutabe also assigns Rinko the aristocratic demon Beelzebub, notorious for his fondness for eating human and dog excrement, as well as Undine, a mermaid demon whose jealousy can quite literally turn the world around her upside down.

And that is far from the full list of demons the young Rinko has to work with while carrying out the agency's many assignments. Demons, however, face one very serious problem in the form of angels who dream of purging the world of evil magic: if an angel manages to get hold of a demon's grimoire, the demon bound to it will be destroyed. Azazel himself looks like an ordinary little dog. He loves to pester Rinko and other women, yet insists that he has no desire to put much effort into relationships with the fairer sex. How will he help his new client?