Tall Kaori and short Sota are siblings by marriage. One day, commanded by Kaori, Sota becomes the dorm manager and coach for her university women's volleyball team. Among the members is Ayano, his first love, and they have an unexpected reunion! Sota begins living together with the club members as the dorm manager. But that night, he witnesses an unexpected side of Ayano, whom he's always admired...?!

Kaori, who had suggested the date herself, becomes flustered upon learning that Sota and Ayano went to a hotel. Still, as Sota's sister, she tries to mediate between them... Meanwhile, Sakura, Kyoka, and Yuria, having heard the whole story, come up with a bizarre theory: Since they're also members of the girls' volleyball club like Ayano, they should have the right to do the same thing! And so, they begin seducing Sota!

Everyone is present at the girls' dormitory, now with the club president, Sanae, who had been absent for a while due to family circumstances, returning to the volleyball club. Sanae, a libero specializing in defense, is petite despite being on the volleyball team, and Sota finds himself drawn to her, who is shorter than him. The group decides to hold a Genghis Khan party to celebrate Sanae's return and Sota's appointment as coach. But that night, an unexpected hint of romance awaited Sota!

Sakura is always full of jokes. One day, when Sota tells her that she'd be cute if she just acted normal, a certain memory resurfaces. Back in elementary school, Sakura, already tall for her age, played the clown while spending her days with her male friend, Takeshi. Eventually, they entered middle school and both joined the volleyball club. However, a rift gradually formed between Sakura, blessed with physique and talent, and Takeshi, who was not...

One night, Kaori, wearing only her underwear, comes to Sota's room seeking help. Sota is shocked, but it turns out the club members were holding a strip mahjong tournament. With Kaori facing certain defeat, she makes a last-ditch effort to recruit Sota as her substitute player. The tournament's grand prize was... the right to do whatever they wanted with Sota?! Reluctant but needing to protect himself, Sota joins the game. Meanwhile, Kaori seems to have her own thoughts on the matter...

Last night's events left Sota feeling awkward. Kaori forcefully tries to act like nothing happened, but Sota's words about Sanae stirs something within her. Amidst this, a secret about Kyoka is revealed?! While it was quietly known among the club members, the shock of it coming out causes Kyoka to flee. Mental care is also an important job for the dorm manager and coach... Sota hurriedly chases after her!

The gym gets double-booked by both the volleyball and basketball teams. They decide to settle it with a game, and the sport Julia proposes is none other than basketball?! There's no way they stand a chance against the basketball team at their own game, and naturally, the members voice their discontent. But Julia is strangely confident, and Sota decides to trust her. And so, the match between the volleyball team and basketball team begins!

The girls from the dorm head to the shopping district for supplies. They came to buy groceries, but Sota gets thoroughly swayed again by the members' self-indulgent, free-spirited actions. After much commotion, they manage to finish shopping and discover they can try their luck at a lucky draw. The grand prize is a pair of hot spring trip vouchers! Kaoru, concerned about Sanae and Sota's relationship, wins it and wants to give it to them, but...

Today is Valentine's Day! Kaoru and Kyoka, with their tall figure and short hair, are treated like princesses and receive chocolates from their female fans. Seeing this, Sanae and Ayano decide they want to make some for Sota too, and eventually the whole club ends up making homemade chocolates. Kaoru also hands Sota the chocolate she made herself. It contains something not found in ordinary family chocolates...

Kaoru couldn't shake the words Ayano had said to her on Valentine's Day night regarding her feelings for Sota. Then, in a sudden turn of events, Kaoru finds herself running out of the dorm in her nightclothes. Sota, who had followed her, invites her on a date. They go clothes shopping together, eat dinner, and drink out. But then, drunk, Kaoru declares she doesn't want to go home...!

The unexpected date with Sota begins. Fueled by alcohol, Kaoru ends up going into a hotel with him, reminiscing about their childhood. Tall and nicknamed the "Witch of Toyohira," Kaoru often protected the smaller, bullied Sota. Kaoru advised him that if he really fought back, things will work out—but that advice relied on Kaoru's own physique. What is the surprising suggestion Kaoru makes to Sota who has half-given up...?

Kaoru and Sota both return to the dorm in the morning, in a mess—Kaoru hungover, Sota with facial injuries. Kaoru had almost no memory of the night, but vaguely recalls that something good had happened. Amidst this, in front of everyone, Julia eventually makes a remark that Kaoru likes Sota?! This happy harem story set in Hokkaido comes to an end for now!