The lecherous Ataru Moroboshi isn't very noteworthy, but his extreme bad luck stands out like the horns on an alien's head. Ataru is chosen to represent humanity in a combat against one of the Oni when a fleet of alien invaders known as the Oni approach Earth. The fact that the duel is actually a game of tag and that Ataru's opponent is Lum, the leader of the Oni's daughter, who values her dignity more than winning, is a stroke of luck for Ataru, as he discovers by taking Lum's bikini top and with it, victory. However, tragedy strikes once more when Lum interprets Ataru's commitment to marrying his fiancée Shinobu Miyake as a wish to marry Lum herself and opts to wed Shinobu instead. likes the concept She moves in with him while using her influence as an extraterrestrial princess. Ataru must reconcile his deteriorating relationship with Shinobu while maintaining Lum's happiness while dealing with the repercussions of his womanizing tendencies, all the while flirting with every woman he meets.