Jester was Maria Asagi's adoptive uncle and her caretaker for the majority of her youth.
Jester had worked as a sweeper of Millennion and was close to Big Daddy. On one hit, however, he had killed the parents of the infant Maria and out of remorse, took Maria in and swore off his job in the organization, making a peaceful living instead. Big Daddy's high regard for Jester even after the nearly two decades that followed implies that when Jester quit being a sweeper, they parted on amicable terms; Bear Walken adds that Big Daddy would not be happy about his death upon witnessing said death by Mad Dog Ladd.
Jester raised Maria into a polite young woman and disapproved of her relationship with Brandon Heat, finding the young gangster to bring too much trouble to her. Maria on her part offered to find Brandon a respectable job, but was refused by Brandon, who saw the prospect as a betrayal to his friends.
Eventually, Brandon goes to Jester to seek aid after his friend Jolice is killed and his gang forced into hiding. Still wary of Brandon, but understanding that his life was at risk and that his death would bring Maria considerable grief, Jester gives him a gun and explains his past in raising Maria, telling him to leave town to keep Maria safe. Deed arrives in a car with his friends and aims a gun at Brandon, but Jester's superior experience enables him to swiftly knock the gun out of Deed's hands with one shot and then intimidate him to leave by firing shots at his feet. However, Jester is soon shot and killed in a surprise attack by Ladd, who disapproved of his brother's cowardice and arrived to finish the job.
Maria mourned her uncle's death, never knowing their true relation. Big Daddy would later take her in to carry on what Jester was unable to finish.
Anime Episodes 2 and 3