Ayuko Uehara spends her last day of summer by going around town for a bit. She soon meets two girls at a Taiyaki bar, Saki Iwasawa and Kanaka Amaya, the latter of whom bumps into her and knocks her taiyaki over. Kanaka apologizes by offering Saki's spicy taiyaki and they both run off. Ayuko overhears that they are starting high school the following day and remarks that she is as well. That night Ayuko ponders that her school uniform is a bit to large for her but that she'll probably grow into it.

On the first day of school, Ayuko has trouble reaching her shoe locker. She is approached by Saki and Kanaka who remember her from the taiyaki bar. Noticing her plight, Kanaka gets down on her knees and offers to be a step-stool for Ayuko, but is ignored by Saki who being tall enough, reaches the locker and helps Ayuko. Afterwards they introduce themselves to each other as they walk to class and then chat about nicknames after finding their seats.

As Home Room begins, their teacher, Sumiko Yamashita gives them a surprise pop quiz which contains the question, "What is your teacher's name?" Mei Yanase is the only one to answer correctly and is made the class representative as such. Kanaka is also made the MVP for her answer "Hikaru Jingūji." which Sumiko feels suits her better. Afterwards, at lunch, the girls once again discuss nicknames. After school, Ayuko tries to get Sumiko's attention by calling her "Jingūji-sensei," but switches to "Yamashita-sensei" when she doesn't respond.

Kanaka shows up at Saki's house to pick her up for school and begins playing with the doorbell, angering Saki. Kanaka decides to race Saki to school, but takes a wrong turn and ends up at her brother's junior high school. When she arrives at Iroha High School, Saki is already at the gate. At the same time, nearby, Shūsaku Matsune-sensei, catches Misuzu Wakatsuki-sensei wearing a student's uniform and is initially fooled. However, as she explains to him the compliments the uniform gets her, Matsune-sensei makes her wear a lab coat to easily tell her apart from the students. He is then approached by the tardy Yamashita-sensei who tells him that their school has a lot of weird teachers. As Matsune-sensei demands an explanation for her tardiness, Yamashita-sensei asks him about his hair.

Kanaka calls Saki on a morning and over the phone it sounds like she is being attacked. As Saki leaves for school, she finds Kanaka on the ground seemingly dead and steps over her, as Kanaka wakes up. On their way, Kanaka remarks the Saki is the type of person who would ignore a "dead" friend, but Saki says that if it were Ayuko, she would do everything she can to bring her back to life. While at school, they bring Ayuko into the pointless discussion and Kanaka explains that she was "attacked" by a 12 foot tall man with an ax but somehow managed to overpower him and afterwards Ayuko showed up and "stabbed" her. As they ask Ayuko why she "stabbed" Kanaka, she says because she was irritated, which Saki agrees with. Finally, Ayuko apologizes for "killing" Kanaka.

Kanaka continues to pretend she's dead in front of Saki's house, but this time, Saki ties her up. As Testing Week begins at Iroha High School, the students are let out early and Kanaka invites Saki and Ayuko over to her house to "study". Since Kanaka's room is not particularly welcoming to guests, the girls spend their time in her brother Sōta Amaya's room, much to his mild irritation. As Sōta is introduced to Ayuko, he asks her if Kanaka is giving her any trouble to which she responds that she is "alot of fun" after a long pause. Sōta eventually settles down to study for his own tests, while the girls continue relaxing, with Kanaka claiming they're just "warming up".

Sōta tries to study while Kanaka and Ayuko continue playing Jenga. Kanaka invites Sōta to take a turn in the game, and while he tries to move a brick, the tower crumbles. Being the loser, Sōta is pressured by Kanaka and Ayuko to buy snacks and drinks. He even discovers that Saki isn't really asleep since she tells him what drink she would like. Later, Sōta returns with the snacks and drinks and he and Saki play a PSP game, with the latter remarking that if she scores badly in her tests it'll be Sōta's fault. The next day, the girls once again show up in Sōta's room. Irritated he goes to clean Kanaka's room so she can entertain guests there, to Kanaka's appreciation but Saki remarks that Kanaka is a terrible sister.

Kanaka tries and fails to get Saki to join any school club with her, since she aspires to be called the "Captain" of something. Ayuko comes along and agrees to try out for clubs with Kanaka. At lunch, Kanaka tells the girls about her failure to find a suitable club. Ayuko and Saki try to narrow down what type of club Kanaka would be best suited for but Kanaka reveals to them that she has no particular talent. While Kanaka sulks, Saki and Ayuko call her "Captain" to lift her spirits. Kanaka then decides to aim to become the Student Council President, although Saki teases that the government may not allow that.

Kanaka tells Saki and Ayuko about a dream she had where they were at the beach smashing watermelons, but Saki became sad because she didn't get to smash any. Ayuko follows by explaining that in her dream, Kanaka was doing a magic trick with her hair, but when Ayuko pulled her left ponytail it resulted in an atomic explosion. Saki follows by telling them that her life dream is to marry into wealth. Saki and Ayuko are put into a state of disbelief when Kanaka reveals that she dreams of being an idol due to the low expectations of her mother and former junior high school teacher. Afterwards Kanaka asks Ms. Wakatsuki how to marry into wealth, which upsets her.

Ms. Wakatsuki continues to wear the student's uniform, but misunderstands that Mr. Matsuno wants her to only wear the lab coat causing her to label him a pervert much to his shock. Later on, Kanaka goes around and asks Ayuko, Ms. Yamashita and Saki questions while covering their eyes, although Ms. Yamashita fails to recognize her, while Saki elbows Kanaka in the stomach. Afterwards, Kanaka asks Mei followed by Saki and Ayuko what high school girls actually do to which Mei responds that they study, to Kanaka's disbelief. Ayuko suggests that they probably talk about love, although Saki and Kanaka twist her words making it seem that Ayuko has romantic feelings for them.

On a rainy morning Saki lazily decides to skip school and become a NEET but grudgingly gets out of bed when Kanaka postulates that a NEET is beneath herself. Saki teases Kanaka's rain boots although they keep her dry while Saki is forced to remove her own soaked socks. When Kanaka takes a picture of Saki's bare legs, Saki breaks her phone. Afterwards, Ms. Yamashita contemplates the pros and cons of the commute to school before declaring the semester over without teaching her students a single thing. Later Kanaka laments that the rain should wash away all of her non-existant problems. Summer vacation begins the next day and Kanaka continues to play with Saki's doorbell much to her irritation.

Summer vacation begins and Ayuko receives a text asking to meet up with Kanaka and Saki. The girls then spend the day doing some of the same things Ayuko had done by herself at the end of the previous year's summer. Afterwards the girls spend the rest of the day at the ocean, enjoying the sunset together and promising to meet up the next day. While drying off at her home at the end of the day, Ayuko looks at the starry sky.