The Minami sisters, Makoto, Touma, Fujioka, and Takeru go on a hot spring trip for New Years.

Kana decides to help her sister become the Great Bancho once more by making the Kana army, but Chiaki on the other hand couldn't help because she considered her friends useless. In the end of the episode they find out Haruka was just refusing a phone call to become class rep.

Chiaki's classmates invite themselves to the Minami home for a group homework session and sleepover. Kana declares it a 'pyjama festival' and puts herself in charge of hospitality, to Chiaki's annoyance. To feed all her guests, Haruka prepares a family-style nabe meal, and she invites Fujioka and Makoto to dinner. Everyone has a good time, but no-one gets much homework done.

During a routine garbage disposal trip, Haruka encounters a boy of Chiaki's age named Fuyuki who is warmly praised by his neighbors for his willingness to freely volunteer his assistance. It is during this encounter that Fuyuki's participation in the weekend neighborhood clean-up is mentioned. Kana's reluctance to take part prompts Haruka to force her and Chiaki to also participate. Later on, Kana summons a few of her classmates, as well as Chiaki's friends to lighten the workload. During the actual clean-up event, it becomes apparent that the work crew Kana assembled was so that Kana could watch while everybody else does all the work.

Kana and Chiaki break a glass rabbit necklace that Haruka had bought. Worried that the rabbit was a gift to Haruka that she treasures, both Kana and Chiaki try to repair the rabbit. After the repairs go badly, Kana tries to get Fujioka, Keiko, and Yoshino to look for another to replace the broken rabbit. In the end, Haruka discovers the truth.

The power goes out and the Minami sisters invite Fuyuki over.

It's Valentines Day and the Minami sisters are making chocolates to give out. Kana tries to eat Fujioka's chocolates, but he tries to keep them a secret from her, hoping that Kana will give him chocolate.

A local shop owner gives Haruka tickets to a new indoor pool. We learn that Chiaki doesn't know how to swim and doesn't want the others to find out. Later, Kana tries to teach Chiaki how to swim and help Chiaki meet her goal to swim 100 meters. Haruka sleeps the entire time, trying to ignore her sisters, until her highschool friends throw her into the pool.

Kana believes she has prophetic dreams and can predict the next nights dinner. Makoto is almost caught crossdressing by Yoshino, and Kana worries whether she is a bad influence on Makoto. Haruka is told that she has been selected to study abroad and is having a hard time with the prospect of leaving.

Spring has sprung and the Minami sisters are sitting around the kotatsu talking. Chiaki confuses 'skirt steak' (harami) with 'flower viewing' (hanami) and is teased by Kana. To save Chiaki, Haruka suggests going flower viewing, though it is still too early.

Toma's secret is almost revealed to Fujioka when he sees her in a girls uniform. Kana covers for her by making Fujioka believe that everyone must crossdress at her place and tries to force Fujioka to comply. Kana feigns a cold on Saturday to avoid doing the city cleanup; Chiaki stays to keep an eye on Kana and figures out she was faking. The next day, she truly catches a cold and tries to avoid being found out, all the while recruiting Uchida and Mako-chan for help.

Chiaki helps to prepare for a school sports meet. Meanwhile, the sisters learn that Fuyuki is moving and is forced to leave in the middle of the sports meet. Kana learns that Haruka has been selected to study abroad.

Frightened of the prospect of Haruka studying abroad, Kana and Chiaki decide to step up to the plate and exert more of an effort with the cooking and cleaning as well as the other domestic chores in order to put Haruka's mind at ease after sending her off with a smile. It quickly becomes evident that the prospect of having to actually take care of themselves in Haruka's absence is much more than Kana and Chiaki can endure. While being tearfully embraced and exhorted to stay with them, Haruka explains to Kana and Chiaki that she has no intention of studying abroad anyway.

A euphoric moment of Haruka securing Chiaki's kimono gives way to frustration that Kana is oversleeping along with the consequent compensatory frenzy thereof that does not seem to bother Uchida who (at the cost of her micro-economy) has been enjoying herself at the festival. The fortune that Uchida purchases with Kana's money only amplifies this fact; unfortunately, Uchida takes the fortune too seriously and overlooks that realizing a fortune takes effort on her part. The next arc features Chiaki contrasting fried noodles and their instant-cup brethern with Touma who has no idea what Chiaki is telling her until Haruka returns home with Kana and prepares some tea that Takeru enjoys using old leaves rather than the ones from the first harvest. The arc that follows thereafter details the home visit the school nurse regarding Chiaki who is none too thrilled with the prospect and that Haruka refuses to intercede as Chiaki's guardian. Between Takeru's obliviousness and the school nurse's flirting along with Kana watching the whole thing, poor Chiaki is absolutely mortified. The final arc details Takeru availing a superstition that points to Kana pulling her usual pranks and a fact that has been demonstrated all throughout.

Touma pays the Minami sisters a visit with an unknown payload whose revelation Chiaki objects in Haruka's absence. Though she inhibits herself for the time being, Kana begins to succumb to avarice when Fujioka comes for a visit. What follows is an exercise in game theory in which Kana leads Chiaki through an enigmatic scenario to obfuscate her volition for having the entire payload to herself since Haruka's estimated arrival time is an unknown variable. Kana's only mistake is that she forgets to consider all the players. The next arc features Haruka and Chiaki being rather vague and indirect about the supermarket and the route thereof as well as a neighborhood dog giving way to Chiaki encountering a shopping list that she suspects that Kana tampered with. The arc thereafter details Hayami comparing notes with Maki regarding Hosaka before she gets the idea to wield Hosaka's computations as her plaything. Hosaka tries befriending Maki and Atsuko but is puzzled when they swiftly flee. The final arc features Haruka taking notes from a cooking show about the preparation of curry while detecting the necessity of visiting the supermarket. Chiaki taking on this stewardship with the very notes that Haruka was taking earlier ends up inspiring Hosaka and herself an extra spicy curry.

Touma's ecstasy during the homebound commute is quickly extinguished by Natsuki helping himself to the snack consecrated for that purpose. Thereafter, Touma's sudden arrival on Chiaki's doorstep gives way to the revelation that Touma has an ongoing passive-aggressive dynamic with her brothers and paints a dysphoric snapshot of Touma's family. The next arc details how the Minami sisters deal with an abundance of apples. The arc concludes with the Minami brothers prosecuting protracted and complex computations regarding the utilization of the apple Touma brought back with her. The arc that follows thereafter details Haruka conferring culinary counsel upon Natsuki while Kana and Chiaki discuss Haruka and Natsuki first as individuals and then as a romantic couple. Chiaki dismisses the prospect before directing Kana to finish the curry Haruka is making. Unfortunately, the culinary protocols for both Haruka's curry and Natsuki's cookies get interchanged with dysphoric consequences. The final arc is related to the first and details the conflagration of Touma confronting Natsuki who repels his brothers' attempts to come to their sister's aid. In an attempt to guide her through guarding against this kind of misunderstanding, Kana demonstrates to Touma a form of Japanese script that looks a lot like arithmetic.

In spite of being the reason for Touma's earlier »Hands off!!!« repulsion, Kana decides that Touma is getting out of hand while making the same mistake with Chiaki at dinner. Haruka swiftly answers the dominance question between Kana and Chiaki right before Touma arrives again with a slideshow of her family government. Kana gives Touma a photograph to show Natsuki that causes a computation crash. The next arc depicts the Minami brothers discussing what to give Touma for her birthday and revealing that Natsuki is the second-generation Banchou that has gotten into a misunderstanding with one of his classmates Hitomi who is fishing for insight regarding maturity and thinks that she can determine Natsuki's thoughts via eye contact.

Chiaki is down in the dumps at the upcoming stewardship of the pool and decides to enliven things by challenging everybody to a game of tag with the »it« person having the garden hose. Makoto stealing the hose and Chiaki's retaliation sparks a three-way water fight with Uchida and Yoshino that obfuscates the issue of Chiaki not being able to swim and that the compensatory computation thereof backfiring on Chiaki. The next arc is a snapshot of Kana's computations of the intermediate school social ambiance in terms of a outing to a public pool followed by the computation crash wrought upon Fujioka regarding appropriate male contact with females and the aftermath thereof. Touma demonstrates her perspective on the issue only to find that male-to-male contact is much more straightforward and has greater latitude.

A euphoric beach outing having the dysphoric prologue of Kana being carsick is reflected upon warmly by Uchida and Yoshino who have taken the whole experience in stride. Yoshino remarks that Chiaki has become attached to Fujioka as an elder sibling in much the same way that Kana has with Uchida and her. Chiaki's exhortation for the whereabouts of her teddy bear disrupts the reminiscence; fortunately, Fujioka brings it back and Kana successfully obfuscates her role. Maki tempers her disdain for her summer homework by successfully wielding Fujioka's computations as her plaything until Kana and Chiaki extinguish her machinations. The next arc features Uchida having a near-complete computation crash as she struggles to complete her summer homework without Chiaki's counsel as the penance for abusing Chiaki's goodwill. Fortunately, Chiaki is not heartless; she eventually relents after seeing Uchida and Makoto's demonstration of interdependence being a two-way street. The final arc features Kana's attempts to forestall the approaching autumn backfiring upon her as Chiaki, galvanized by all the pranks Kana played on her, retaliates by eating Kana's dinner in addition to her own.

Frustrated and bored with the practice for the three-legged race, Chiaki decides to call it a day much to Makoto's dismay. Kana tells Makoto of Chiaki's dearth of sports proficiency and warns that helping Chiaki will jeopardize his transvestite mirage. It becomes obvious that Makoto and Chiaki have not learned to synchronize with each other and that Makoto's transvestite mirage is quite the Damocles sword for Kana to maintain as is demonstrated when a mishap with soda leads to Kana and Chiaki sparring with parables that teach a physical metamorphosis is not a prerequisite for a euphoric relationship. Chiaki accidentally breaking the Minami sisters' mugs sets the stage for a labyrinth of complex and unnecessary strategic game theory computations that conclude to Kana's detriment.

During the homebound commute, Uchida and Yoshino's stopover to buy some baked yams during the homebound commute gives way to Kana explaining to them her »Laws of Popularity«. Availing a bunch of soda cans, Kana directs Uchida and Yoshino through an exercise with soda cans to practice the Law of Weakness Appeal. Unfortunately, Chiaki (especially after the soda geyser) is not amused at the exhibition and Atsuko is put on the hot seat after Haruka takes Maki away. Touma imparting an emphatic »Watch where you are going!!!« punch to a contrite Makoto before walking away ultimately demonstrates that male-female interaction is as a kaleidoscope and that there are a myriad of variables in play. While Kana spends the next arc fishing for iconoclastic responses, Atsuko shares her »cool when silent« perspective of Hosaka before later comparing notes with Maki leads into a comical social sequence in which Hayami and the approaching Hosaka along with Maki and Atsuko seem to have completed these cerebral computations without verifying the results with the outside world.

During a lazy afternoon, Kana decides to help herself to some oranges while Touma and Chiaki read at the kotatsu before getting the idea to snack on an orange. It is not long before Makoto and Uchida learn the root cause: Kana delivering a preemptory »Hands off my oranges; go get your own!!!« karate chop to both Chiaki and Touma. Another arc has everybody galvanized by the Yuletime ambiance: Chiaki synthesizing a huge stocking and leaving it to chance what present she receives, Touma learning to appreciate »useless/annoying« family rituals, and Hosaka acquiring a part-time job as a cake salesman dressed in a Santa Claus suit even though he does not encounter Haruka by that avenue as per his daydream. Haruka hosts a Yuletime banquet at her house.

Caught up in a sudden rainstorm, Touma is forced to make an emergency stopover at Chiaki's house but finds that the hospitality comes with a price: Chiaki refusing to lend Touma any clothes due to her abrasive conduct. Though she initially misinterprets Natsuki's counsel on her conduct, Touma finally catches the lesson -- and a set of clean clothes. The next arc features Chiaki's lack of discretion and foresight with her affinity for trivia and facts. Fortunately, Fujioka helps Chiaki put her error in this area into perspective. The arc that follows thereafter details the prologue of the social dynamic Fujioka is involved in with both Chiaki and Touma: Chiaki mortifying Touma out of Fujioka's lap. The arc after that details that Natsuki has the same problem of abrasive conduct about which he earlier lectured Touma who enters the room and seats herself at the table. However, Natsuki's attempts to heed his brothers' counsel along with Touma's opinions of the Minami sisters sour the ambiance.

Fujioka approaching Kana with a book for Chiaki and Riko computing the approach thereof gives way to another girl named Hiroko taking notes of the whole scenario from afar before conscripting Riko into an exercise to build up the courage necessary for a confession that flounders. The next arc details Kana conducting her volition of a study session at her home with Keiko and Fujioka that Riko decides to capitalize upon. The study session's academic success contrasts with the fact that Riko has not once confessed her feelings seeming content to enjoy the ambiance of proximity to Fujioka. Fujioka, Riko, and Keiko nearly have a computation crash when they go into the bathroom to find the bathtub covered in order to keep the water hot and decide to shower instead. The arc the follows thereafter details the epilogue of a recent test in which Riko, Fujioka, and Kana's test scores are close to Keiko's perfect score. The final arc begins with a conversation between Makoto and Touma over being given chocolates as a Valentine's Day joke prompting Kana deciding to play Othello after telling Chiaki that she needs to practice celebrating Valentine's Day to gain the experience.

Chiaki lashing out at Uchida, Kana, and Maki due to their boisterous laughter rousing her from a nap on a warm spring day gives way Kana first sending in Uchida and Maki to fight this battle for her before doing her own dirty work only to have it end in a stalemate. The next arc features Makoto and Uchida taking an afternoon nap with Kana when Maki pays the trio a visit with the request that Kana gaze upon her sleeping face while recalling a dysphoric middle school memory, especially after Kana reads Maki and Uchida sleeping as the perfect opportunity to draw on their faces as a prank. The arc thereafter features Haruka and Atsuko looking at pictures from their middle school days. The arc that ensues has Chiaki sewing on a wayward button while Kana detects Haruka's school uniform carelessly strewn about before remarking of the seasonal uniform transition. While modifying a shirt of Kana's, Chiaki accidentally slices Haruka's fuku skirt. Knowing that Haruka will be very angry with them when she detects the damage, Kana and Chiaki attempt some desperate and frenzied repairs to buy time for computing their next move. Unfortunately, things coming unraveled when Maki detects the telltale thread put both Kana and Chiaki in scalding hot water with Haruka. The final arc features Kana blowing up at Chiaki for insulting her once too often before deciding to resolve her fears of Chiaki becoming a delinquent by being a nice older sister. Unfortunately, all Kana accomplishes is to greatly unsettle Chiaki and frighten her into co-sleeping with Haruka.

While doing some homework, Chiaki observes Haruka in some kind of distress and anxiously runs to Kana for assistance. Even though she feels that the cause of Haruka's distress is something minor like what to prepare for dinner/breakfast, Kana observes Haruka with Chiaki for a while without gaining any more insight unaware that Haruka is observing their strange behavior and wondering its root cause. While Kana and Chiaki converse after school, Haruka is doing the same with Yoshino and Uchida. The misunderstanding is ultimately resolved by everybody making faces at each other. The next arc features the aftermath of a nightmare that has Chiaki clinging to Kana that Haruka euphorically takes in stride. While Haruka is out on the town with her friends, Chiaki gets over her nightmare while Kana has a similar nightmare that sends her clinging to Haruka who is late coming home. The final arc is set in motion when Kana writes her Tanabata wish to repudiate sweets that gets interpreted as a suicide note that scares both Haruka and Chiaki who think that they are to blame. Fortunately, the misunderstanding is quickly resolved and everybody has a wonderful time at the Tanabata party glad to be together.