Wataru Kaneda is an ordinary high school student who also works part-time as a programmer. As he begins his second year, Wataru naively assumes nothing out of the ordinary will occur, allowing him to concentrate on his job. However, his ideal school life is suddenly disrupted by three girls: Tamayo Ougi, Rika Aikyou, and Sanae Mayuzumi. All three claim that, based on a pact made ten years ago, one of them is destined to become his fiancée. To make things more complicated, the trio moves into the same apartment floor as Wataru, a situation that irritates Tomo Kurebayashi, his childhood friend who harbors feelings for him. As the girls press him for attention and a final decision, Wataru must determine how to resolve this predicament.