Who is DL Chastain from Vineland and what is their importance?

DL Chastain is a martial arts expert and ninja, DL Chastain is the daughter of a military family that moves around the world. While in Japan, she is approached by a martial arts instructor who teaches her the secret ways of the ninja, including how to kill with a touch that takes a year to work. She is recruited by mobster Ralph Wayvone to assassinate Brock Vond while posing as a prostitute, but accidentally gives the death touch to Takeshi Fumimota, who has been sent in Vond's place after the plot was discovered.