Okusama ga Seito Kaichou! S01E01 - The Student Council President Marries into a Family

During the student council election speeches, Ui Wakana promises a liberalization of love, tossing condoms to everyone and wins by a landslide, to the dismay of her opponent Hayato Izumi, who becomes her vice president in the student council. After returning from cram school, Hayato discovers Ui in his apartment. She declares that she is his wife because their parents had drunkenly arranged for them to get married when they were 3 years old.