Miki Koishikawa's ordinary life as a high school sophomore is turned upside down when her parents suddenly announce that they are getting divorced in order to swap partners with a couple they met in Hawaii. They seek her approval of the shocking change, and at a dinner where Miki meets the other couple as well as their son Yuu, who is about her age, she reluctantly agrees to the arrangement. Yuu, while at first a jerk who takes every opportunity to make fun of Miki, turns out to be fun and attractive, and Miki finds herself falling for him. Little by little, she accepts her new family arrangement, and opens up to Yuu as they become friends.