Natsu no Arashi! Akinai-chū

One day, everyone gathers at Cafe "Hako-bune", where Arashi and Hajime are working, and they discuss about the summer tradition. They end up planning to go to the beach, and Hajime is overjoyed because he will be able to see Arashi in her swim suit. Arashi, Kaya, Yayoi, Kanako are all having fun choosing swimsuits from Master's collection. But Jun, misunderstood as a boy, is having a hard time trying to keep his cover. The following day, they go to the beach in Yamashiro's car. Drawing men's attention, playing with the creatures, each one of them enjoys their summer.

After having fun at the beach, they came to an inn. They enjoyed themselves by going to saunas, outdoor hot springs, and playing mahjong. With Arashi's "kindness," Jun ends up sharing a room with Hajime. To keep her secret, Jun ends up buying men's underwear, and avoiding the bath. But in the end, Jun gets caught by Hajime and gets dragged to the bath. Arashi and Kaya save Jun. With Arashi's proposal, they end up doing a courage test. Arashi and Jun coincidentally pair up. Jun asks Arashi how she feels about Hajime.

Sucked of his life essence on a daily basis by Yayoi and Kanako, Sunglasses is somewhat groggy. Arashi proposes that only one of them use him as a source of energy supply, so Yayoi tries to find someone compatible with her from today's customers at Hakobune. Since Yayoi is shy with men, she struggles to respond back to them. With his dog, Yamashiro arrives at the café. Everyone at Hakobune urges Yayoi to go talk to Yamashiro, but, panicking, Yayoi runs away.

One day in the pouring rain, Yayoi and Hajime take the day off from work at the cafe and go over to Jun's house where Kaya is staying. Jun finds out that Hajime is coming over and panics to conceal her secret. In the midst of her panicking, Jun ends up wearing a wedding dress. Jun finally finishes hiding her underwear and such, though she forgets to hide the family portrait at the front door. As she dashes to the front door to get the portrait, the door opens, and she falls into Hajime with her wedding dress still on...

During her shift at "Hako-bune," Kanako, all of a sudden, gets dizzy and drops the salt shaker. When Kanako borrows some glasses from Arashi, she is surrounded by a bright light, transforming her into a maid warrior. Disregarding how Kanako feels, Hajime and the others, wanting to see her transform again, try to get Kanako to wear the glasses again. All of a sudden, "Hako-bune" has turned into a cosplay party for the girls.

On a very hot day, the Master comes up with a plan to prepare cold noodles. The staff at "Hako-bune" tries to recreate the amazing cold noodles that Arashi had tried once when she was young. The girls struggle in making the noodles since Kanako and Yayoi have never tried cold noodles, and Arashi does not know the exact recipe either. When it was left up to Kaya, she ended up making noodles topped with shaved ice. On the other hand, Arashi ends up creating a Neapolitan. It takes a turn for the worse when they start running the noodles in the rain gutter.

The Master panics, not knowing where she put the ceramic bowl. According to the Master, the bowl that had a bounty of one million yen at "Hako-bune" was gone all of a sudden. Arashi and the others go to search for the bowl using their time leap powers. When they arrive in the past, they find the master just wearing an apron and running around with the bowl. In the end, the master remembers that she had given the bowl to Yayoi for safe keeping, though Yayoi forgets where she placed the bowl.

On a hot day when mirages are appearing, Hajime and the others are searching for the remote control for the air conditioner. After they search through "Hako-bune," they find a pile of remote controls and start testing them. The one for the air conditioning is nowhere to be found, and it gets hotter and more uncomfortable. As it gets hotter, Kaya notices that Arashi is acting funny, and she becomes scared of her. As the number of remotes to test dwindles, Arashi can no longer bear the heat and goes crazy.

Hajime and Arashi are hanging out having fun. As Jun observes this, she refers back to the time when she talked to Arashi at the grave site. Jun remembers that Arashi tells her: "I will be gone once summer ends.” Arashi gets asked out on a date by Yamashiro in the meantime. Trusting in their "bond,” Hajime is not fazed by this. Jun believes that Hajime is too carefree about this situation. Thinking that Hajime does not know that time with Arashi is limited, she tells him that he will only be able to be with Arashi in the summer.

Arashi rejecting Hajime might have caused the two to not to be able to connect anymore. With Hajime being in a rut, Yayoi explains to him that it might have been the age difference that caused a misunderstanding between the two. Coming up with the idea that if both of them were the same age, they may be able to understand each other better, Hajime, Yayoi, Kanako, and Sunglasses time travel to when Arashi was 13 years old. Once they arrive in the past, Hajime and the others are overwhelmed by the mansion that Arashi lives in.

One morning when Jun woke up, her body was that of a grown woman. Arashi was the only one that noticed right away, though none of the others knew who she was. To get out of an awkward moment, she tells the others she is the older sister of Jun, by the name of Ryoko. When approaching Kaya to tell her the truth, Jun learns that they are planning a surprise birthday party for her. Jun ends up helping the preparations for the party. While helping the preparations, Hajime compliments on how beautiful she is, but Jun gets annoyed as the older Jun is being compared to the younger Jun.

Arashi was asked by manga illustrator, Anamori, to act out a kissing scene that will inspire her to draw the scene. First, Kaya was chosen to be her partner for the scene, but the scene failed because Kaya’s breath had the smell of gyoza. Yaoi and Kanako followed, but they were not able to successfully act out the scene either. Hajime and Jun tried to act out the scene, but this was stopped by Arashi. The place turned into chaos as Sunglasses and Yamashiro were called out to do a kissing scene.

For some reason Kaya was laying on the counter face down. Arashi suspected Hajime of doing something to Kaya seeing that she glared at Hajime every time she picked her face up. Arashi asked Hajime if anything happened, though Hajime does not recall doing anything. Kaya was actually trying to find a moment to get back at Hajime for making her drink the “Cutie Cherry Fruit Juice.” Kaya starts making something with the Kiwis that Sunglasses brought in, but Hajime and Arashi follow in taking strange actions.