Asuka Kasen is a leader of the Japanese Yakuza. She acquired this position in her gang through her expertise in gaining information with torturing. It is also hinted she is bisexual and a masochist. She and her brother Kenji arived in Liberty City in 1991. Asuka is a good friend of Maria Latore, despite of the fact Maria is the wife of Salvatore Leone, the don of the rival Leone Family.
Mike meets Asuka after the mission School's Out, in which Asuka's niece Yuka was rescued by Mike after she was kidnapped by the Colombian Cartel. After this, Asuka helps Mike finding Vinnies murderer.
When Maria saves Claude from walking into Salvatores trap, she introduces him to her friend Asuka. Asuka helps Claude escaping to Staunton Island and shows him a safe house. She offers Claude to work for the Yakuza, but first he has to prove his ties with the mafia are broken by murdering Salvatore, which Claude does.
Later, Asuka and several other Yakuza members raid a Panlantic construction site which is used as a front by the Colombian Cartel to sell SPANK. She captures Miguel, who she believes is responsible for killing her brother although Claude was the murderer, and tortures him to gain information on Catalina and the Colombian Cartel. She is killed by Catalina when the Cartel attack the construction site to regain their territory.