"I won't let you pay them! Those assholes don't deserve our money"
Yuya is a host who works at Stardust. He is one of Kiryu's allies.
Yuya first encounters Kiryu outside Stardust, looking to meet the owner of the club, Kazuki. He perceives this as subterfuge against the club, taunting Kiryu for trying to threaten the club. Kiryu simply repeats his request and adds that he is not from any Yakuza group, which causes Yuya to lash out.
Yuya apologizes Kiryu for not knowing he was not a yakuza anymore for Kazuki. Yuya argues Shimano's boy to kicking them out from Stardust. Yuya won't let Kazuki pay Shimano's men,Kiryu helps out fighting them off.
When Kazuki is shot and spends his time at Emoto Clinic, Yuya becomes interim manager.
At the beginning of the game, he is cleaning the mess in front of Stardust when Kiryu and Haruka come and say goodbye to him. In the end, he and Kazuki catch Hamazaki, who stabs Kiryu.
Following the line of last game, Yuya has become almost a minor character with little to no involvement to the game main story. In Yakuza 4, Yuya has become the manager of Stardust, with Kazuki standing behind Yuya's decisions. He is involved on two substories. Still, he cherises his friendship with Kazuma and is glad to have him back once again in Kamurocho.
Yuya met Kiryu on the streets of Fukuoka when Kiryu was talking with Muramatsu, not knowing that Kiryu now lives under an assumed identity. To avoid being identified, Kiryu tried to play dumb, but he later told Yuya that he lived under an assumed identity to protect Haruka's career as a pop idol. During the meet, Yuya revealed that he wants to quit the business as he sees that Stardust is already an established business and that he went to Fukuoka to distance himself from Stardust.'
A while later, he told Kiryu that he now works as a live-in waiter at La Seine, a local hostess club and changed his name to Kazuki. He told Kiryu that the club's manager suffered from harassment from local yakuza. Much to Kiryu's disappointment for knowing that Yuya didn't do his best to protect the business, he punched Yuya in the face to knock some sense into him, causing both men to fight the yakuza and Yuya reclaiming the extortion money. In the end, he revealed that he's actually the manager of Stardust and is going to leave La Seine.
During Kiryu's return to Kamurocho from Hiroshima, Yuya met him in front of Stardust. Initially, Kiryu didn't recognize him until he removed his spectacles. He revealed that he now quit Stardust because the Koreans bought the business and becomes an ordinary office worker. While meeting him, Kiryu tried to gain information about a man named Tatsukawa, who works as a host in Kamurocho according to Tagashira's account.
Yuya is protective when it comes to his club's business, but otherwise a quick-tempered person with a strong hatred to the yakuza. He's initially hostile to Kiryu, but later becomes a good friend to him.
- Yuya's seiyuu would go on to voice another character related to the Yakuza, [Seto] in Seto no Hanayome.