Keima Katsuragi, a second-year high school student, is an avid dating sim gamer. He is known on the Internet as "The Capturing God" for his legendary skills to be able to "capture" any 2D girl in games. However, in his actual school life, Keima is known as otamegane, a derogatory portmanteau of the two words otaku (オタク) and megane (メガネ-"glasses").
At the start of the series, Keima receives an e-mail offering him a contract to "capture" girls. He accepts what is thought to be a challenge, and a demon from Hell nicknamed Elsie appears. She asks for his cooperation to help her in catching the runaway spirits. These spirits hide themselves inside the girl's heart, and Elsie suggests that the only method to force the spirits out is by "capturing" their hearts—making them fall in love. Appalled by the idea, Keima refuses after clarifying to Elsie that he is only interested in "capturing" 2D girls and that he detests reality. Nevertheless, with the contract already accepted, Keima would have to help Elsie no matter what; if they fail, both Elsie and Keima would lose their heads.