Kazuki has waited ten years for the day her neighbors moved back into their old house. She has a crush on Yuuji, whom she considers her first love, but she never managed to express her feelings to him before they moved away. When they were children, Yuuji often came over to play with Kazuki, Kazuki's older sister Hatsune, and Yuuji's sister Marie. Her ideal image of Yuuji was soon shattered when he turned out to be more than she had expected, acting all ecchi during their reunion. With their parents off in South America, both families must learn to live with each other and rekindle the childhood feelings they shared. Things get even crazier as they attend the same school.