Ataru is looking for a part-time job for the winter. He finds an ad for a job at a bathhouse, but while looking for the location, he has to go through a long, narrow, and clutter filled alleyway, which transports him to a subspace.
Lum organizes a year end-party by transporting all the students into a historical world, where each student impersonates a different historical character from Japan and abroad.
Onsen's had it with his students' shenanigans, and he's threatening weekend detention if they make so much as a peep in class. The class is determined to avoid detention at any cost, even as Ten shows up to harass them.
Lum's father got kicked out of the house for greedily eating both his and his wife's food. He has to crash at the Moroboshi's on Earth until things blow over, but now the big guy's eating them out of house and home.
Ataru and Lum plan a ski trip. Naturally, she's happy to go wherever he goes if it's just the two of them. However, Ataru has other plans when they get to the slopes. His classmates find out about their trip, so they follow Lum and Ataru.
Ryoko invites everyone to a masquerade ball. The prize for what appears to be best costume at said ball is a kiss from Ryoko herself. She doesn't tell them that it's actually a masquerade-combat ball. It's exactly what it sounds like.
Lum catches an alien cold virus from her father and goes to school wearing a face mask. Pervert classmates pay Ataru to bring the mask to them in order to virtually kiss Lum by wearing it, but they didn't account for the consequences.
Ataru confides to Megane that he is "giving up", and has chosen him as successor. Megane is elated as he imagines having Lum all to himself. Shinobu, having overheard their conversation, imagines that with Ataru out of the picture, there would change in the class' balance of power would result in her losing Mendou to Lum, causing repercussions far beyond Tomobiki High. She then conspires with the popular girls from the surrounding schools to stop Ataru and protect the status quo.
The new girl in school, Ryuunosuke, who was raised and still dresses as a boy, becomes infatuated with Ran and asks her out on a date, which Ran agrees to not knowing Ryuunosuke is actually a girl.
A few of the school students go camping, but due to Lum's cooking being too spicy for human consumption, they have to search for another source of food, which lead them to a magical place.
Now that she's no longer bound by Ataru's kiss, princess Kurama is looking for a beautiful man and sets her eyes on Ryuunosuke, so her team of wise crows sets out to turn Ryuunosuke into a man.
Mendou's childhood rival Tobimaro Mizunokouji appears to challenge him to the ultimate baseball game, and Mendou's sister, Ryouko, who has maintained a crush on Tobimaro, will help him win by any means necessary.
Ataru writes and directs his first movie starring Lum, after getting his classmates to pitch in to fund the project. But after running out of ideas, he gets multiple students to participate in front of the camera, and chaos ensues.
After his parents leave for a three day vacation, Ataru and Lum spend a hot summer day in his house, which somehow evolves into a psychic fight between Sakura and Cherry.
Teacher Onsen tells Ataru's class about the seven school ghosts and the legend of the deadly spirit of the school's willow tree. Ataru unknowingly incurs the wrath of the tree, and all types of shenanigans follow at school late at night.
Jariten's mother comes to Earth to visit him, but he's absolutely terrified. His mother is a dedicated firefighter, responds to fire bells almost instantly, and deals with arsonists and pyromaniacs with sadistic brutality.
