Hayato Izumi is a studious, responsible and down to earth person who is running for student council president. To his dismay his is completely outmatched by Ui Wakana who wins in a landslide after promising comprehensive sex education, free condoms and other exciting reforms. Defeated but not discouraged, Hayato swallows his pride and settles for vice president. Ui, that very night, shows up at his place and says that their parents made a drunken promise decades ago that their children would one day marry. Ui and Hayato must now try to balance school life with married life, keeping their relationship secret from the rest of the student body and learning to coexist with each other.