Jin Miyamoto was a corrupt cop who occasionally fed information to Jake, and changed ways to help Katagiri against the Yakuza.
In season 1, Miyamoto worked for Tozawa and hid a supply of drugs from the police during a raid.
He took advantage of Jake during his early days and was generally a very apathetic cop who didn’t believe in changing.
After the failed raid, Katagiri suspects that Miyamoto is a Tozawa mole and he asks his superior if he can set up a sting.
He later tells Miyamoto that he’s gathered evidence against Tozawa and placed it in the evidence room.
Miyamoto sneaks into the room to find the evidence but it turns out to be a trap as the box is empty and a surveillance camera is set up to catch him in the act.
Trying to do the right thing
Katagiri confronts Miyamoto, reminding him of his integrity as a dedicated officer with the potential for redemption through good deeds.
They decide to collaborate, aiming to compile evidence against Tozawa. Miyamoto starts to leak fabricated information to the Yakuza leader.
However, when a supposed tip-off about a drug shipment turns out to be bogus, Tozawa confronts Katagiri.
Tozawa ominously warns Katagiri that his and his family’s safety is at risk if he continues to pursue him, adding that he has already “dealt with” Miyamoto.
Subsequently, an anonymous individual delivers an envelope to Katagiri at the station, which contains a hotel matchbook featuring a room number alongside Miyamoto’s name.
Arriving at the hotel, Katagiri discovers Miyamoto’s deceased body in the room, arranged to suggest a heroin overdose, complete with needles protruding from his arm.
Among Miyamoto’s belongings, Katagiri finds a photograph evidencing their collusion to undermine Tozawa.
It becomes clear that Tozawa orchestrated this “accident,” yet Katagiri receives orders to discontinue his investigation.
Upon briefing his superior about their covert operation, Katagiri faces reprimand for not disclosing their strategy earlier.
The media, manipulated to report Miyamoto’s demise as a heart attack, obscures the true circumstances of his death. Nonetheless, Tintin receives a hint suggesting there’s more to the story.
Katagiri confides in Jake about the ordeal, cautioning him against publicizing the details or discussing them further.
Jake endorses the heart attack narrative to mislead Tintin and protect the investigation’s confidentiality.