High schooler Natsuo is hopelessly in love with his cheerful and popular teacher, Hina. However, one day at a mixer, he meets a moody girl by the name of Rui and ends up sleeping with her. Soon after, his father announces that he's getting remarried to a woman with two daughters of her own. And who shows up in tow, other than both Hina and Rui?! Natsuo's outrageous new life starts now!
After leaving Natsuo, Hina starts over in a new town. Then one day, the man she once had an affair with, Shuu, appears before her eyes. Meanwhile, unable to cope with his growing affection for Rui, Natsuo finds himself on a rollercoaster of emotion.