Kyon returns home from a tiring day, only to have his little sister reprimand him for leaving her alone and forcing her to play with a now-unconscious Shamisen. Once Kyon falls asleep, the SOS brigade appear in his New Year's Dream, with Koizumi, Yuki and Tsuruya appearing as Mt. Fuji, an Eggplant and a Hawk, respectively.
Kyon first arrives at the clubroom, only to be deafened by Haruhi who is throwing a tantrum because she is bored, which drives away a client. Shortly thereafter, Kyon finds Yuki playing an eroge on her laptop with the volume turned up. Kyon provides her with a set of rabbit-shaped headphones to keep the 'questionable sounds' from being heard in the room. Shortly afterwards, Kyon is accosted by Ryōko Asakura who attempts to kill him, but is stopped by Yuki. Before she fully dies, she informs Kyon that there are others who will attempt to kill him besides her, only to be interrupted by an exasperated Kyon, who nonchalantly states "the butler did it".
Mikuru finds the clubroom deserted, with a TV set on the table. Mikuru turns it on, to find she is the audience of a local quiz show, in which Haruhi is the host, and Kyon and Yuki are the contestants. However, Haruhi's attempts of making the quiz more local go a bit too far, resulting in Kyon being killed (then revived) by fireworks and a truck. Meanwhile, Mikuru ignores the show and instead plays with her small lion-like pet.
Mikuru finds out that Yuki is viewing erotic images on her laptop, but is too embarrassed to tell what she's seen to Kyon. Several weeks go by, and several changes are noted. Kyon finds that the bookshelves in the room are being filled with video games, and Haruhi begins to notice Yuki wearing cosplay outfits. When Mikuru finds the outfits, a cosplay war breaks out. Meanwhile, Ryoko has revived herself, but in a foot-tall chibi form. Eventually, Yuki finds out, and after saving the miniature Ryoko from a hungry cat, allows her to stay with her at her apartment.
The computer club challenge Haruhi to a dodgeball game in the hopes of retrieving their laptops, but Haruhi decides to play a real game of dodgeball. Her reality-altering powers allow all the players to use 100% of their abilities.
Mikuru informs Kyon of extra outfits found on the clothes rack in the corner. When informed that they belong to Yuki, a small-scale cosplay 'war' breaks out. At the end of the day, Yuki finishes an anime series she has been following, and lends her collection to Kyon. Mikuru grows upset when she sees the lead character of the series is a maid, scaring her into thinking Kyon is into 'maid moe'. Ryoko is annoyed at how Yuki keeps putting her in baby things, although can't help but fall victim to her idea of fun.
Haruhi holds a sport contest. When asked to bring 'a barrier to the heart' as part of a scavenger hunt, Kyon brings Koizumi over and tells him 'I love you', causing Haruhi to faint. Taniguchi lags behind in the events whilst Kyon gets used as a makeshift tug-of-war rope.
Haruhi holds a 'Close Encounters of the Third Kind' Spring Festival, in which she dresses Taniguchi as a demon and gives him food whilst everyone goes outside and celebrates. Yuki traps Ryoko and forces her to dress up in an outfit for Hinamatsuri.
Haruhi asks for ideas for a screenplay and ends up writing about otaku maid warriors with a month to live fighting to the death, which somehow leads to Kyon exploding.
After a small half-asleep scuffle with Ryoko, Yuki heads out for a Sunday morning with the SOS Brigade. Ryoko tries to clean the apartment to take her mind off things, but grows upset being stuck inside. Using an umbrella, she manages to try and leave the building (to kill Kyon and provoke a response from Haruhi, as per her original mission), only to return to the apartment when a cat hungrily eyes her.
Yuki hides Ryoko in a little box before Haruhi, Mikuru and Tsuruya come over to make Valentine's Day chocolates. Haruhi's plan to make a life-size chocolate Mikuru is deemed impossible, so the remaining chocolate is fashioned into smaller sculptures, truffles, and small chocolate cakes. Once the 3 girls leave, Yuki lets Ryoko out of her box, and shares a chocolate cake with her.
Valentine's Day is upon the SOS Brigade, and the girls have chocolates for Kyon and Itsuki. However, they have to 'earn' their presents. The two guys leave and return, dressed as hosts in flashy suits and 'handsome' poses, which does nothing but make Mikuru cry.
Haruhi decides to celebrate Halloween, but knows nothing about the event, using a single image as reference. Sometime later, Yuki takes Ryoko to the supermarket and helps her out in cooking dinner. Ryoko later scolds Yuki for playing games late at night.
Haruhi and Kyon have a small battle involving balloons and blow-guns. However, when Mikuru wanders into the room, she is used as the unwitting victim of a balloon-decorating contest, with Itsuki as the judge. Meanwhile, Yuki finds some extra un-inflated balloons, and decides to take them home.
Using the balloons she got from Kyon, Yuki makes Ryoko a living balloon dog, although its creation is a little horrifying. Whilst having fun with it, Ryoko walks into another trap laid by Yuki, with assistance from the dog, who suddenly talks and calls himself Kimidori. Ryoko is attached to balloons that Yuki filled with hydrogen, which causes the balloons to detonate in a large explosion when one of the balloons is heated by a ceiling light.
Haruhi hosts a 'simple and healthy' cooking show, which to her means boiling instant noodles for ridiculous amounts of time. During the commercial, Kyon tries to practice with a katana Yuki had with her, but it ends up being too much for him.
Kyon is joined by Mikuru, Tsuruya and Yuki, who find a stone that Yuki breaks, releasing a spirit. Whilst trying to figure out how to dig his hole, Kyon is interrupted by Arakawa who "randomly" stops by, and Mori who creates a giant crater. Unable to explain the situation to Haruhi, Kyon takes all the credit.
Curious about the motives of Santa, Haruhi sets Kyon to keep watch for him whilst everyone else has a Christmas Party. They encounter Taniguchi, who dressed up as Santa to return an unwanted Kappa he stole from the computer club. When Haruhi sees (bit doesn't recognize) him, her powers transform him into what she envisioned Santa to look like and chases him until he is apprehended by Yuki and Tsuruya. He escapes, but returns to normal.
Ryoko and Kimidori try to pull a prank on Yuki, but she is totally oblivious. Whilst trying to get Kimidori out from under a fridge following one of their attempts, he bursts, devastating Ryoko. It turns out, she had been punk'd by both Yuki and Kimidori.
Haruhi, Mikuru, Yuki and Tsuruya attend a mall exhibition whilst Kyon and Koizumi attempt a puzzle. Tsuruya fights against one of the show's monsters, who is really Mori, but is inevitably defeated. In the wake of the clash, Kyon and Koizumi's puzzle is ruined, leaving them frozen in place.
Ryoko scolds Yuki and Kimidori for being so carefree and gets them to help with the cleaning. After it is done, Ryoko becomes curious as to why Kimidori is in a kite, and joins in their fun.
Feeling a little bored on their own, Ryoko and Kimidori discover a present from Yuki to relieve their boredom, which turns out to be a bomb. In order to save Ryoko, Kimidori carries the bomb outside before it explodes. Yuki returns and everyone is alright, although Kimidori is slightly brown.
Haruhi and Kyon try to decide on a new look for Mikuru, although their figure drawing skills are incredibly bad. Tsuruya helps out. Afterwards, Yuki shows Kyon that she has made a dating sim of the SOS Brigade, which is surprisingly full of bad ends.
