PaRappa is just your ordinary talking dog; he enjoys spending time with his friends, listening to music, and going on adventures. Together with his friends, PaRappa gets into many strange situations, all the while learning to navigate through life, get along with his friends, and pine for the girl of his dreams, Sunny Funny. Among Parappa's friends are Katy, the blue cat, PJ, the lazy bear, Matt, PJ's friend from Club Fun, Paula, a sassy fox girl, and Sunny Funny, the flower and PaRappa's love of his life. Parappa's adventures range from the ordinary to the bizarre. He crosses paths with the two mischievous baddies, Gaster and Groober, helps resolve questions of friendship and love, and even goes on trips through time itself. Nothing can change Parappa's positive outlook on life.

Seventeen-year-old Nanaka Kirisato is a high school student serious about her studies and goals in life. She frequently criticizes her best friend, Nenji Nagihara, for being a childish delinquent who spends his time fighting other boys. Then one day, after a heated argument with Nenji, she falls off a flight of stairs and suffers a brain injury, resulting in her mind reverting to that of a six-year-old. With this in mind, Nanaka's father and Nenji must keep her injury a secret as she struggles to live a normal life and grow up all over again.