Following the events of Daa! Daa! Daa!, Ruu is now a cheerful youth residing on his home world, Planet Otto. Then, a bewildered girl named Miu arrives from Earth via a wormhole. Ruu teams up with her and vows to return her home. Unbeknownst to Ruu, Miu is the daughter of the very people who cared for him during his time on Earth.