The world gods knows

The series follows the exploits of Keima Katsuragi, an intelligent, gloomy teenager who is known on the Internet as "The God of Conquest" for his legendary skills to "conquer" any girl in Bishōjo games, yet does not like girls in real life, where he is known as the Otamegane (オタメガネ), a derogatory portmanteau of the two words otaku (オタク) and Megane (メガネ, lit. glasses). One day, out of pride, he accidentally accepts what he assumes to be a challenge for a Bishōjo game when in reality he has accepted a contract from a bumbling demoness named Elsie who asks for his help in capturing runaway spirits from Hell who are hiding in the hearts of girls. The only way to force the spirits out of the girls hearts is by replacing the spirits in the girls' hearts with himself (metaphorically speaking) by making the girls fall in love with him, much to Keima's horror. With the threat of death for both of them should he refuse, Keima has no choice but to help Elsie.