Ataru Moroboshi is a hilarious and fickle boy, causing no end of troubles. One day, he is chosen as the representative of the earth to fight in a crucial game. His opponent is an attractive alien called Lum, from the Planet of Ogre.
Because Shinobu, whom Ataru likes, tells him “I will marry you if you win!”, he pulls out all of his strength and wins the game. However, contrary to his expectation, Lum is the one who storms into Ataru's house to become his bride!
Tomobiki town has already had enough strange people, but Lum, her alien friends and spaceship crowd into the town. The whole town is tossed upside down by Lum, Ataru and their weird friends. This is a SF comedy story based on popular comics drawn by Rumiko Takahashi.