The whole series has been building to three words Ataru refuses to say, and this movie finally makes him choose between his pride and everything he claims not to care about. Lum knows what he actually feels. The question is whether he knows it too. After decades of running, tag stops being a game and becomes the only honest conversation they've ever had.

Lupa, one more suitor claiming to be Lum's fiancé, turns up, and this time the whole planet is on the line. To keep Earth from being wiped out, Ataru and Lum must replay their game of tag. There is a catch: Ataru can only win by telling Lum "I love you," three words he has always refused to say to her. Now everything hinges on whether he can admit how he truly feels, or whether his pride will doom the world. Adapted from the final story of the manga, this movie brings the comedy, romance and sci-fi antics of Urusei Yatsura to their climax.