Keima Katsuragi, a high school student and self-proclaimed "God of Conquest," excels at dating simulation games, where he can effortlessly capture the hearts of virtual girls. However, his real-life social skills are severely lacking, and he dismisses the concept of real-world romance as inferior to his games. His life takes a drastic turn when a demon named Elsie contracts him to assist in capturing "runaway spirits" that have escaped from hell. These spirits hide within the hearts of real girls, causing emotional instability, and the only way to expel them is by making the host fall in love.

Keima reluctantly agrees, using his gaming expertise to "conquer" the hearts of various girls in real life. Each arc focuses on a different girl, with Keima employing strategic methods to identify and resolve their emotional conflicts, thereby freeing the spirits. As the series progresses, the narrative evolves from episodic romantic conquests to a more interconnected plot. Keima encounters recurring characters, including other demons like Haqua, who assist or challenge him, and the mysterious Chihiro, a girl who complicates his detached approach to relationships.

The story introduces deeper lore about the demon world and the origins of the runaway spirits, revealing that their escape is tied to a larger conspiracy. Keima’s role expands beyond mere spirit capture as he becomes entangled in conflicts involving the demon realm and its hierarchy. The stakes escalate when Keima discovers that his actions have unintended consequences, particularly regarding the memories of the girls he has helped. A central mystery emerges involving the "Goddesses," powerful entities whose fragments reside within certain girls, further complicating Keima’s mission.

Character dynamics shift as Keima’s relationships with the girls and his demon allies grow more complex. His initial indifference to real-world emotions gradually gives way to a deeper understanding of human connections, though he remains reluctant to fully embrace them. The series balances humor, romance, and supernatural elements, with a focus on Keima’s growth and the evolving challenges he faces. The narrative culminates in a climactic resolution involving the Goddesses, the demon world, and Keima’s own emotional journey, tying together the various threads of the story.