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.

The invasion of an alien race known as the Oni begins a new life for Ataru Moroboshi, a lecherous trouble-making tenth grader in the small town of Tomobiki. After unwittingly proposing to the Oni princess Lum Invader instead of his sweetheart Shinobu, Ataru becomes a conduit for aliens arriving on Earth, causing all sorts of havoc for him and his companions, not to mention his own reputation!

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.

As the perpetually lecherous Ataru and his friends prepare for a carnival at Tomobiki High School, they gradually realize the days are literally repeating themselves. Any effort to break the pattern dumps them back where they started.

Featured special that uses scenes from the series stored on a personal satellite of the Los Mendo family.

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.

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.

Ryoko throws a tea party for her friends. Flashbacks reveal the pasts of Ryoko's various guests.

Yagami comes to Maison Ikkoku, not knowing of Godai's and Kyoko's wedding, stating that she is now an adult, which she is, not knowing how to tell her, they panic, but she finds out in the end, and is heart broken.

The sole survivor of the original massacre comes face-to-face with Bubba and his sadistic clan one last time.