— Seishiro Munakata
"Some people are users, the rest get used. It's always been that way. People must know their place."
Seishiro Munakata is the Deputy Commissioner of Tokyo Metropolitan Police forces and the main antagonist of Yakuza 4. He is a corrupt superior of the police force and aims to control the criminal empire through the law enforcement.
Holding the second highest rank in the police force, Munakata is extremely greedy and manipulative. He desires the power to control crime through Law Enforcement and will do everything necessary to achieve his goal. Munakata mainly uses his position to blackmails higher-ranked officers to do his dirty works such as Sugiuchi and Hisai, and even manage to persuade Daigo into having Majima arrested. Munakata even went as far as ordering Arai to kidnap Kiryu's orphanage children in an attempt to weaken him so that he can get the 100 billion that Akiyama possess without him interfering. He was also the true mastermind behind the Tojo Clan's missing 10 billion incident in which Jingu was actually planned to send the money straight to him so that he can built more illegal prisons and paid off criminals to commit crimes to his own advantage.
Throughout his appearance, he wears a standard police outfit. His hair is fully black in 1985 but by 2010, his hair is visibly graying.
In 1985, a detective named Junji Sugiuchi gave him the report of the Yoshiharu Ueno hit. However, he knows that the report was fake and that the hit was actually a set up by Isao Katsuragi. He then blackmails Sugiuchi into introducing him with Katsuragi so that his fake report can be written as true.
At some point, he's using his influence to send an officer named Hiroaki Arai to go undercover as a member of the Tojo Clan's Kanemura Enterprises to infiltrate the clan. He was also involved in the missing 10 billion yen incident in 2005 at the events of Yakuza before, and had many secret funds which he used to build illegal prisons and control criminals. Munakata also pressured Sugiuchi and Chief Hisai to work for him to do his dirty works.
In the end of Chapter 3, he ordered one of his men to kill Sugiuchi before he can leak anymore informations. He also send Hisai to kill Masayoshi Tanimura and his accomplices. Although Hisai decided to commit suicide rather than following Munakata's orders.
In Chapter 4, he manage to persuade Daigo to let Majima get arrested and offered to work together with him as Katsuragi planned to betray him by blackmailing him with the file. In finale, Arai returns to Munakata and handed over the file that consist of his connection with the missing 10 billion dollars. Although he was grateful that Arai retrieved the file and Kiryu eradicated the Ueno Seiwa, he scolds Arai for not taking Akiyama's money with him. In an attempt to get the 100 billion yen from Kiryu, he orders Arai to kidnap the children at Sunshine Orphanage to weaken him. However, Arai betrays him and shoots Munakata with the revolver.
However, it turns out that Munakata anticipated Arai's betrayal and the revolver bullet is only plastic rounds that was used for riot control. He later appears to confront Arai, Kido and Daigo on top of the Millennium Tower with his highly trained, special forces bodyguards to claim the money. Suddenly, Kiryu, Saejima, Akiyama, and Tanimura arrive to deal with their enemies. Tanimura takes him on as the final battle and swears to avenge his father, Sugiuchi, and Hisai. Although Tanimura was seriously outnumbered, he manage to defeat all of Munakata's bodyguards. Munakata cowers in fear as Arai and Tanimura threatens him. However, Munakata laughs at the odds of him being arrested as the entire Justice system could have cover up a man in his position practically, taunting that arresting him will put Japan to chaos by the blow to Police's public relation. Only to see the reverse of situation when Akiyama calls in Date and allows him to scatter newspapers that made his corruption public before any intervention can be made, thanks to the copy of the file that Arai retrieved. In frustration, Munakata shoots Akiyama and gets disarmed by Tanimura. Luckily, the last pack of his money saved Akiyama from the bullet. After being utterly defeated, Munakata shoots himself with Arai's pistol to avoid arrest.
Munakata relies only on his bodyguards to protect him while he attempts to attack you from a far range with his gun, he tends to run from you when you get close to him. Munakata either calls his bodyguards to attack you when you keep defeating his bodyguards, or he can sometimes call back his bodyguards to protect himself while the bodyguards try to attack you.