It is the story of Ataru Moroboshi, and the alien Lum, who believes she is Ataru's wife after he accidentally proposes to her. The series makes heavy use of Japanese mythology, culture and puns. The series was adapted into an anime TV series produced by Kitty Films and broadcast on Fuji Television affiliates from 1981 to 1986 with 195 episodes. Eleven OVAs and six theatrical movies followed.
Plot Summary The series begins when aliens from the planet Oniboshi invade Earth. They agree to leave only if Earth's champion can defeat the Oni champion in a game of tag within a ten-day time limit. Earth's champion, randomly selected by the aliens, is Ataru Moroboshi, a Japanese teenager with highly overactive hormones. The alien competitor turns out to be the curvaceous Lum, so Ataru relishes the idea of having to catch this beauty. However, his attitude changes when he discovers that Lum can fly. When things start looking desperate for the Earth, Ataru's girlfriend, Shinobu offers to tie the knot if he succeeds, and on the last day, when he finally catches Lum, he declares his intentions to be married. Lum misunderstands this as a proposal and eagerly agrees, since she has become smitten with Ataru. He tries to disengage himself, but Lum is adamantly faithful and demonstrates a willingness to use her natural ability to generate electric shocks to keep her "husband" in line. Later in the series continuity, Lum and some of her alien friends become more-or-less regular residents of Tomobiki and interact with the natives, who are interesting in their own right. Urusei Yatsura is unique for its premise, its immense cast of characters, and its free-for-all, anything-can-happen attitude.
It introduced many elements that are taken for granted in today's anime, such as yandere/tsundere characters, the harem concept, using pop songs as OP/ED, using pop culture and current fashion as part of the story.
I've watch many anime and quotes few harem series, but this man is the first and luckiest of them. Even if he has to ensure Lum's electro shocks.