Tsuyoshi and his lecherous friend Tsukasa are fleeing from Tsukasa's younger sister when they run into a time machine. Together with its inventor, they end up accidentally sent twelve years into the past. There they come face to face with their own childhood selves, and with Tsuyoshi's sister as she was back then, long before she became the rough, violent tomboy they know today. The film is a comedy with touches of drama, romance and everyday life.