Lum, Ataru, Megane & Co. are holding a party to celebrate the 1st anniversary of her arrival on Earth. After Ataru openly gripes about his life with Lum, she gets up and leaves. She can't be found, and it's feared she's left Earth for good.
Lum's alien friends keep popping up at school, and disappearing right before Lum can have a chance to talk to them. Now her feelings are hurt because she feels she's being left out of whatever they're doing.
Lately the students of Tomobiki H.S. have been sneaking off campus to eat at the local eateries, and the faculty, led by Onsen, is conspiring to stop them at all costs. It's all-out war, with restaurant district as its battlefield!
Ataru invites Lum and a few of his schoolmates for a hike at a remote spot known for having many fossils. Meanwhile, a documentary film crew are looking for any subject to shoot at the same location.
The sleeping princess Kurama whom Ataru kissed and woke up previously returns with her crow guardians seeking a new man to kiss and wake her up from her second sleep.
Ten-chan infects Ataru with an alien type of tooth cavity which spreads through physical contact. Soon after, Ataru's entire classmates start attacking each other to spread the cavity, and chaos ensues.
Ten brings a huge cat home with him, and he takes an immediate liking to Ataru's kotatsu (foot warmer), and sits on the staircase with it. It's dinnertime, and Ataru can't come downstairs to eat without getting pummeled by that darn cat.
Ataru saves a crane caught in a trap hoping for it to repay the favor in accordance with a legend. The crane turns into a raccoon, visits Ataru's home, and tries desperately to repay the favor.