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.