Mendou, is the richest boy in Japan, he is the heir to the Mendou fortune. Every girl in the class wants him, and he can have any girl he wants, but the one girl he does want, he can't have, that is Lum, her devotion is totally to Ataru. For that reason, Ataru is Mendou's main rival. The simalarities beetween Ataru and Mendou, are more than what Mendou would like to admit. They are both ruthless womanizers, each in different ways, Ataru goes in head first, and Mendou uses politeness, and his charm, Mendou usually being the more successful.
Mendou, is claustrophobic, and afraid of the dark, but those fears are nulled when there are women around, the second that the women don't look at him, he goes crazy with fear, and when, there are no women around and he's in a dark cramped place, it's funny to see how he reacts.
Mendou, always carries a kitana around, and if you piss him off enough, he'll pull it out at a moment's notice, ready to strike at you.
Mendou is another interesting character in Urusei Yatsura