Lupika, an alien princess, is in love with a tofu seller. To make him love her too (at least, announce his love. He obviously fears the social taboo of a tofu vendor marrying a princess), she needs to get a love potion, which is in a certain temple. Legend has it that the only person that can obtain this love potion is the most lecherous man in the universe. That man turns out to be Ataru Moroboshi. Lupika kidnaps Ataru to make him get the potion, and Lum and her friends go out to search for Ataru.

It seems that Lum's grandfather made an agreement that should he have a daughter, she would be married to a traveling merchant that he met. Now, the merchant has come to collect due. Ataru is tricked into thinking that Lum wants to leave, and so, in a moment of anger, says he hates her. Arguments erupt, and Lum decides that she must know the truth of Atarus feelings. As for all the questions of importance for the Onis, a game of tag begins, one that Ataru can win simply by telling Lum I Love You. However, in the end his pride may end up dooming him. So begins the series of events that will at long last decide the future and fate of Ataru and Lum.

Urusei Yatsura: Only You is a romantic comedy movie based on the manga and anime series Urusei Yatsura. The story revolves around Lum, an alien princess from the planet Oniboshi, who crash-lands on Earth and falls in love with Ataru, a high school boy. However, Lum is not the only one vying for Ataru's affection as he already has a girlfriend named Shinobu. As Lum tries to win Ataru's love, hilarity and chaos ensue. The movie explores themes of love, relationships, and misunderstandings in a comedic and lighthearted manner.

The third film finds Ataru transformed into a pink hippopotamus, which sends Lum chasing after the wicked magician responsible, with catastrophic results. With Lum gone, her friends decide that there is no reason to remain, and so Tomobiki slowly returns to normal. The highlight of the film is a high speed chase scene with an angry Lum flying after the mysterious Ruu through the city at night and into a hall of mirrors (and illusion ). Ataru's true feelings for Lum are probably more obvious in this film than any of the others.

While performing in a student film, Ataru cuts down Tarozakura, a large, ancient cherry tree. Strange things begin to happen all across Tomobiki: a mountain appears out of nowhere, spring changes to winter, and Lum loses her powers, while those around her act as if she doesn't exist.

In Urusei Yatsura: Beautiful Dreamer, the residents of Tomobiki town wake up to find that they are trapped in a reality where time loops and dreams blend with reality. As they try to figure out what is happening, they must face their deepest desires and fears. The boundaries between dreams and reality blur, leading to a captivating and surreal adventure.