Two sets of parents divorce and marry each other, while their children Miki and Yuu are caught in the middle and start falling for each other.

Miki's parents are getting divorced. Why? Because her parents bumped into another married couple, and found that each other's partners suited them better and plan to remarry. While this upsets Miki, the other couple's son, Yuu, doesn't seem to mind this at all. Now all six of them live in the same house and while Miki doesn't like this arrangement, she can't get Yuu out of her mind...—Annonymous

The sophomore high school student Miki Koishikawa finds out that her parents are getting divorced in order to swap partners with a couple which they met on their recent vacation in Hawaii. Miki is worried about her own living arrangements. She is told that both new couples will inhabit the same big house, and that she will live with both her parents and her new step-parents. Miki is also introduced to her new step-brother Yuu Matsura, who is close to her own age. Yuu initially is primarily interested in teasing and pranking his new "sister", but the two teenage step-siblings are increasingly attracted to each other. Miki's male best friend Ginta Suou is secretly in love with her, and he tries to drive a wedge between Miki and Yuu in order to have a chance with her. Yuu's ex-girlfriend Arimi Suzuki is trying to regain his affection, and she is not pleased that he has another love interest.—Dimos I