Monchichi-chan, the twin sister, loves her twin brother very much. She is a crybaby and always follows her brother. Monchichi-kun, the twin brother, protects his sister. He is a brave adventurer and a fishing champion but sometimes becomes a hasty boy. They enjoy wonderful and mysterious adventures together every day. When they take a space walk, they ride on a swan of the swan constellation and build a small house with aliens in space. They can do everything children want to do and dream of. This heartwarming animation series featuring the pretty twins surely gives wonderful dreams, brother-sister love and hopes for the future to all the children in the world.