Izumi Hayato, as member of the student council strongly opposes the president Wakana Ui's "strong push for the liberation of love" at their school. But her charm reaches her fellow students and also the other student council members: treasurer Fujisaki Karen and secretary Niikura Ayane.

When Ui makes an appointment with Hayato late in the evening, little does he know what is in store for him: Ui's irresponsible mother in Canada OK'ed not only that Ui take up residence in Hayato's apartment, but also live there as his wife. This came about because Hayato's father apparently asked Ui's parents many years ago to have their daughter marry Hayato.

And so Hayato's bizarre life with the student council president and self-appointed wife begins...

[Source: AniDB]