In the form of a bird-like creature, the elementary school student Punpun lives a normal life and goes to school with other children. From his somewhat naive and childlike perspective, he develops an overflowing imagination. He falls in love with the new classmate Aiko, decides to become an astronomer, and escapes from his constantly quarreling home through his flights of fantasy. Because Aiko has told Punpun that people must colonize other stars in the future to survive, astronomy has become a fixed idea for him - he wants to save humanity. However, if that is not possible, he at least wants to save Aiko. Together with his classmates, he also experiences the typical problems of growing up - awakening sexuality, emotional confusion, and the challenges of becoming an adult.