In the 26th century, humans discover a humanoid race living on the distant world GO/7498/2, a dark-skinned, golden-eyed people who seem to eke out a primitive, carefree existence. However, a scout team from Earth discovers that there is more to them than meets the eye--they live in symbiosis with vicious reptilian parasites, and the Terran scientists have upset the delicate natural balance.

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.