The story begins with Izumi Hayato running to be student body president. But when a beautiful girl swings in promising the liberalization of love while flinging condoms into the audience, he ends up losing to her and becoming the vice president. At the student council meeting, the newly-elected president invites herself over to Izumi's house, where she promptly announces she is to become Izumi's wife thanks to an agreement that their parents had made, a drunken promise decades ago that their children would one day become husband and wife. Naturally Hayato is against this, but Ui has the complete opposite reaction, and even wants to live with him!

Will the upset Hayato and the overenthusiastic Ui be able to manage their school and marital life while keeping it a secret from the other students? Or will the two never come to understand each other's feelings?