Keima is bishōjo gamer who is called "The Capturing God" on the Internet for his ability to capture any girl in any bishōjo game but does not like girls in real life. One day, he accidentally accepts a contract with the demoness Elsie to help her capture evil spirits that have escaped from hell and have hidden themselves in girls' hearts with the only way to force these spirits out is to make the girls fall in love with him. Keima angrily explains to Elsie that he doesn't like girls and his "capturing skills" only work in games but is shocked to learn that both of them will be killed by the magical collars on their necks if he breaks his contract, forcing him to comply. His first target is his classmate, Ayumi Takahara who is training for the upcoming track-and-field meet. Keima cheers her on by displaying banners using Elsie's magical raiment at the field everyday. While Ayumi is annoyed by his actions, Keima believes she will eventually get used to him and like him. After a confrontation with jealous seniors, Ayumi sprains her leg a day before the meet. However, Keima confronts her that night as he figured out that Ayumi faked her injury because her meeting with the seniors made her question her confidence. Keima consoles Ayumi and tells her to believe in herself, which makes her fall for Keima. They kiss when Ayumi keeps Keima from falling down the stairs, forcing the spirit out of her body and allowing Elsie to capture it. Ayumi wins the meet but loses all of her memories with Keima, though she blushes when Keima congratulates her. Much to his confusion, Elsie has transferred to his school, claiming to be his sister.

Keima confronts Elsie on why she’s still here and he still has the magic collar on his neck which the latter reveals that their contract is still not finish and the collar will only be removed until they capture all of the runaway spirits in the city. After meeting Keima’s mother, Mari, Elsie claims she is her “husband’s illegitimate child” which Mari snaps on her husband on the phone for his “infidelity” and allows Elsie to stay with them. Keima however, refuses to accept Elsie as his little sister as in his view, she doesn’t have the requirements that qualify her to be one which she tries to impress him albeit unsuccessfully. But upon hearing her story on wanting to be successful just like her older sister, Keima reluctantly accepts Elsie as his sister. During lunch at a popular food stall, Keima and Elsie find their next target, Mio Aoyama, a rich girl who proceeds to buy all of the yakisoba sandwiches. Keima believes she is an easy target as she has all the characteristics of a Tsundere, and a love confession might break her hard shell. However, the confession doesn’t work as planned, and Mio has her chauffeur beat Keima badly. As Keima and Elsie follow Mio to her home, they are surprised to learn Mio lives in a shabby apartment.

Keima and Elsie eavesdrop the conversation between Mio and her chauffeur and learn that the Aoyama’s family are no longer rich since her father died and Mio’s mother has been working hard to make ends meet. The chauffeur leaves in disgust after the prideful Mio refuses to stop pretending to be rich. Mio catches Keima snooping around and quickly goes back to her apartment. Since Keima is the only one to know her secret, he can use it to get closer with Mio. The next day, Keima becomes Mio new chauffeur by riding her to school in various elaborate bike carriages made by Elsie’s raiment. On the fifth day, Keima, tired of riding Mio current carriage, almost gets whipped by Mio who smiles but quickly reverts to her cold expression and goes home. Keima now decides the next stage of his plans by bringing her to a ball she was invited. At the ball, a dressed up Mio is angry to learn that Keima, now in a tuxedo, actually brought them at the mansion gardens but later teaches Keima how to dance. But after encountering a few rich people who look down on Mio’s current status, Keima finally confronts her that she should stop pretending to be rich. Even though she keeps the act up to keep her father’s memory alive, Keima convinces Mio that she should let go of the past and move on and live her on life for her father and Keima’s sake. Keima kisses Mio and the spirit from her body is captured by Elsie. The next day, Keima and Elsie meets Mio, who now loses her memories of Keima, who has a change of attitude and has accepted her family's status and burns incense for her late father. Yet she still acts prideful and blushes when she sees Keima.

Keima attempts to finish and get the heroine, Sora Asuka from the PFP Bishōjo game "Crayon". But the game has many bugs including one that loops a previous scene over and over again. No making things any better is the fact saving the game only crashes it and game company that made it is now bankrupt thus there are no patches to fix the game. In order to avoid the bug loop and finish the game, Keima forcefully enlists a reluctant Elsie to help record the choices that he made in the game. Elsie is at first confused on why Keima takes the game seriously but soon respect his dedication to help the girls in his games just like the girls he helps in real life. After many attempts, Keima finally manages to avoid the loop bug and goes to the next scene but unexpectedly gets into another bug, resolving him to try again much to Elsie's horror. A wikipedia article about "Crayon" reveals a rumor that someone managed to get the ending, hinting Keima was able to finish the game.