One day, A mysterious alien baby from outer space comes to planet Earth, and only-child Michio Mikita finds him. He takes him as his own child, much to the surprise of his family. As he discovers he can talk (although not perfectly), walk, and do magic, and he causes havoc for Michio with his powers. Like Nobita Nobi from Doraemon (Another manga series from Abiko's friend Fujiko F Fujio), Michio does bad at work and is clumsy, so things go worse when it comes to UB's mischief, even though he's only a baby. The manga and anime tells the story of the duo and their adventures.