- Kazuki: "I'm going to enjoy thrusting my sword into you!"
- Toni: "Yeah...I heard that about you."
- ― Kazuki Kasen and Toni Cipriani before their final showdown
Kazuki is voiced by Keenan Shimizu, who has also appeared in Law & Order.
Kazuki Kasen was born in Japan and moved to the United States with his younger siblings, Kenji and Asuka, later meeting his wife Toshiko. He, at some point,became the leader of the Yakuza. Kazuki began to lead the Yakuza in their attempts to increase their standing in the city, in particular due to the actions of Massimo Torini and the Sicilian Mafia, and bought a casino in Torrington, Staunton Island.
Kazuki, who married Toshiko in a pre-arranged marriage, neglects his wife and spends the majority of his time with his men.
Events of GTA Liberty City Stories
Toshiko, after hearing of Toni Cipriani destroying a Yakuza tank, hires him to destroy and humiliate Kazuki, first by having Toni steal a Yakuza munitions delivery and then destroy Kazuki's casino takings whilst being transferred. Toni later accompanies Toshiko to the opera.
Toni later attacks Kazuki's casino, killing many of his men, and facing him in a sword duel, resulting Kazuki's death. After learning of her husband's death, Toshiko, feeling remorse, commits suicide. After his death, his siblings become the new co-leaders of the Yakuza.
- During the mission A Date With Death, Toshiko states that Kazuki is a samurai. Kazuki is likely to either be a descendant of a samurai or to follow the Bushido code practiced by the Yakuza, becoming a samurai by way of practice and nickname. The official title as a military nobleman was abolished during the Meiji Restoration during the nineteenth century.
- It is sometimes alluded to that Kazuki is a closeted bisexual. When Toshiko tells Toni that Kazuki "prefers the company of his men", she then asks "Do you understand?". Toni later teases Kazuki when he says "I am going to enjoy thrusting my sword into you", to which Kazuki does not respond, and soon after tries to have Toni killed outside of his samurai code of honor.
- Furthermore, on the game's official website, an email is shown from Kazuki to Kenji, saying he feels very guilty about something he isn't telling Toshiko. He writes "Many times, I have killed a man, afterwards, just to keep him quiet", and that "now there is someone special, but I am a man, not a rat, skulking in a sewer". Toshiko discovers the email and sends it to an anonymous forum for life advice.
- GTA Liberty City Stories
- Cash In Kazuki's Chips (Killed)