While playing outside on a rainy day, a little girl peers into a puddle and sees Mudkin, who invites her to become his queen.

In the midst of the rain, rainbows can be hard to see, but with courage and the help of good friends, there is always a way out of the darkness.

Wherever Rain Boy goes, rain follows, and when he is invited to Sun Kidd's birthday party the other children complain that his presence is ruining their fun; now Sun Kidd is hiding in her room because she is upset by her friends' behavior, and an apparently an endless storm has descended on the world--until they all discover that something wonderful happens when rain and sun finally get together.