Ataru Moroboshi is the deuteragonist in Urusei Yatsura He is the most lecherous teenager in the universe.
He is very lecherous with an idiotic personality, and often tries to escape class work. Whenever he sees or hears a pretty girl he immediately asks for their address and telephone number, but never succeeds.
Ataru constantly tries to ignore Lum but it is proven many times that Ataru cares about her, probably only hating her electric shock.
- Lum - Ataru met Lum when he was randomly selected by a computer to represent mankind in a game of tag with the fate of the Earth on the line (Lum herself represented the Oni race). When it looked like Ataru would fail, Shinobu (his girlfriend at the time) promised to marry him if he won. Determined to do "the stuff that married people do", he succeeded in catching Lum and then loudly declared "Now I can get married!!" However, Lum mistook this as a proposal to herself and the two were immediately engaged. In the beginning he is cold-hearted towards her and saw her as a nuisance preventing him from girl hunting, but by the time of the story "A Night Alone!!" (夜を二人で!! , Yoru wo Futari de!!) (Vol. 18) he was completely okay with sharing a bed with her. He is also shown to be quite jealous if another guy gets to close to Lum (ex: Rei, Shuutaro, Shingo, the Dolphin, etc). In the story "The Gloves of Love and War" (愛と闘魂のグローブ, Ai to Tokon no Gurōbu) (Vol. 21), in which he accidentally puts on boxing gloves that force him to grab and punch anyone who gets close enough to him, he continuously puts his own face in front of Lum's each time she gets too close, punching himself instead. This is just one of many instances when Ataru does everything he can to protect Lum from physical harm. Near the end of the series, in the story introducing Inaba, he decides to protect the future where he and Lum get married. In the final story they have another game of tag, this time with the Earth's memory of Lum and everything that has happened since her arrival on the line. Lum will let him win if he just says "I love you", but he refuses and tries to catch her himself. However, in the end, he indirectly says "I'll love you forever" when Lum sees that he had kept something of hers (her old horns). She allows him to catch her and continues to live on Earth with him. In the last panel of the series, Lum says that one day she'll make him actually say it, to which Ataru responds "Only on my deathbed".