Once he arrived, he met Lum Invader, a gorgeous bikini-clad alien princess, for the first time.Ataru had been randomly selected by a computer to represent mankind in a game of tag with the fate of the Earth on the line. Unable to catch the flying beauty, Shinobu promised to marry him if he won." However, Lum mistook this as a proposal to herself, which she accepted, and the two were immediately engaged.Ataru is a 17-year-old student at Tomobiki High School, Class 2-4.
Whenever he sees or hears a pretty girl, he immediately asks for her address and telephone number, but never succeeds.Determined to do "the stuff that married people do", he succeeded in catching Lum by stealing her bikini top and grabbing her horns when she tried to get it back.In his moment of triumph, Ataru loudly declared "Now I can get married!!Also when she leaves for an extended period of time, he becomes very depressed and lonely in her absences.As highlighted in the final story arc, where, even faced with the prospective of losing Lum and all his memories of her he refuses to give in her request of a proper love declaration, most the friction between Lum and Ataru stems from their clashing personalities: while Lum is utterly naïve and innocent about Earth customs and uses, but still truly wishes to be a proper and mature wife for Ataru and a prim daughter-in-law for her family, Ataru is more world-weary and savvy, yet he prefers to act as a flirty, happy-go-lucky teen, thus making Lum doubt of his commitment, Ataru can catch a katana blade with his bare hands.