"Urusei Yatsura: Za Shōgaibutsu Suiei Taikai" is a special episode within the larger "Urusei Yatsura" franchise, centered around a chaotic swimming competition. The story revolves around Ataru Moroboshi, a perpetually unlucky and lecherous high school student, and Lum, a fiery alien princess from the planet Oniboshi who is deeply in love with him. The episode introduces a bizarre swimming tournament organized by the eccentric Mendou family, known for their wealth and influence. The competition, held in a massive indoor pool, attracts a wide array of participants, including humans, aliens, and supernatural beings, each with their own unique abilities and quirks.

The tournament quickly devolves into chaos as the contestants employ underhanded tactics and bizarre strategies to win. Ataru, driven by his usual self-serving motives, attempts to exploit the situation for personal gain, often at the expense of others. Lum, fiercely protective of Ataru, becomes entangled in the madness, using her alien powers to intervene in the competition. Other recurring characters, such as Shinobu, Ataru's childhood friend and former love interest, and Mendou Shutaro, a wealthy and arrogant rival, also play significant roles, adding to the comedic and competitive tension.

The narrative is filled with slapstick humor, absurd scenarios, and over-the-top antics, characteristic of the "Urusei Yatsura" series. The swimming competition serves as a backdrop for the characters' interactions, highlighting their personalities and relationships. The episode balances comedic moments with brief instances of character development, particularly in the dynamics between Ataru and Lum, whose tumultuous relationship is a central theme throughout the series. The story concludes with the tournament's chaotic resolution, leaving the characters in their usual state of disarray but maintaining the lighthearted tone that defines the franchise.