Yoshino, the granddaughter of the local yakuza boss in Osaka, is shocked when she learns that to establish peace between their gangs, she is supposed to become engaged to the grandson of a boss from Tokyo.

The daughter of the president of another subsidiary of the Tokusa group has gone missing, so Yoshino must be accompanied around the clock by Kirishima for her safety.

As she and Kirishima try to figure each other out, some visitors from Kansai cast an ominious light on Yoshino's stay in Tokyo.

After a tense encounter between Kirishima and Shouma, Shouma drives back to Osaka. Yoshino gets the sense that something is spoiling Kirishima's mood and confronts him. Like every year, Yoshino catches a summer flu.

After their final exams, Yoshino and Kirishima head to Yokohama to meet Yoshino's cousin, Tsubaki Akashigata, who recently moved from Kyoto. Reuniting after a long time, the three—Yoshino, Tsubaki, and Kirishima, who tagged along—explore the city together. They enjoy reminiscing and chatting about trivial things as they stroll through Yokohama. However, their fun is interrupted when Yoshino gets a call from school and has to leave, leaving the other two behind. Kirishima seizes the moment and invites Tsubaki on a casual date. Alone together, they find themselves inside the glowing Ferris wheel at night. In this private, quiet space, Kirishima turns to Tsubaki and asks her an important question.

Returning to Japan after living abroad, Nao Shioda lands a job as a TV announcer. She crosses paths with Kirishima, her ex-boyfriend from the past. In front of their friends, the two pretend to be strangers, but when they find themselves alone, Kirishima gently speaks to Nao and hands her his contact information. Meanwhile, Yoshino and Kirishima travel to Osaka. While there, Yoshino reconnects with Shoma after a long time apart. Coincidentally, Nao also arrives in Osaka to attend an event, setting the stage for their paths to cross once more.

From her seat on the bus, Nao spots Kirishima and Yoshino walking together. Unable to ignore them, she gets off at the next stop to follow. However, it's Yoshino who approaches Nao first. The two women begin to talk, and the conversation inevitably turns to their shared connection: Kirishima. Nao reveals to Yoshino some of Kirishima's past that Yoshino had no idea about. Meanwhile, Nao faces trouble of her own. Her ex-boyfriend, Ozu, has uncovered secrets about her past and her previous relationship with Kirishima, gaining leverage that could impact her future. With this power, Ozu makes a troubling demand of Nao—one that could change everything.

The semi-criminal group holding grudges against Yoshino and Kirishima, along with Azami Suou, had gathered under Ozu’s command. While Kirishima was with Nao, Yoshino spotted Ozu and his group and decided to carry out a plan on her own. Upon learning about Yoshino’s situation, Kirishima reluctantly contacted Shoma, the only person he could turn to in Osaka, to entrust Nao to him and head toward Yoshino. During this time, Kirishima called Yoshino, and the two made a significant "bet."

Kirishima finds himself in the crowded chaos of a fireworks festival, while Yoshino and a group of delinquents gather nearby. Yoshino chases after Oz, who has been abducted by Naoya, while Kirishima blends into the crowd and launches a surprise attack on the delinquents. Targeted due to the incident involving Shiori Akaza, Yoshino is spotted by Naoya and faces imminent danger. Kirishima continues to take down the delinquents one by one, but a mysterious and dangerous figure, Azami Suo, suddenly appears before him. "Where is Yoshino Somei?" Azami asks Kirishima. But what is Azami's true objective...?

Azami's true intentions for searching for Yoshino and the words Minami said to Shoma before leaving remain shrouded in mystery as Azami and the others disappear without a trace. Left behind, Kirishima and Yoshino confront Ozu, who has been captured, demanding he settle Naoya's scandals and promise never to interfere with them again. Despite Ozu's skillful maneuvering, always stopping just short of breaking the law and avoiding creating any vulnerabilities, Kirishima sets a trap for him. With the case resolved, Kirishima earns the right to be Yoshino's boyfriend and enthusiastically presses forward, only for Yoshino to propose a certain challenge to him.

After visiting the Somei family grave, Kirishima is invited to the Somei group, where he spends a pleasant time. The group enjoys a barbecue together, sharing stories about young Tsubaki, who looked strikingly similar to Kirishima. Renji, one of Tsubaki's few close friends, reminisces about the past and shares nostalgic tales with Yoshino and Kirishima. However, the atmosphere becomes tense when Hotei returns from work. Summoned to the basement by Renji, Kirishima and Shoma are questioned about the uproar involving semi-outlaw groups that occurred in the Kansai region, a matter that also entangled Yoshino.

After a tumultuous visit to her hometown, Yoshino and Kirishima return from Osaka to the Miyama residence in Tokyo. They thought their usual daily life would resume as always, but from the very next day, Yoshino starts ignoring Kirishima. She alters her schedule to avoid him when going to school, ignores him when he speaks, and offers no response even when he cooks for her. A rare moment of distress overtakes Kirishima, who sits in the rain in front of the annex where Yoshino is staying. What is the reason Yoshino continues to ignore Kirishima...?