The "Killer of 99" is Shungiku, a convicted murderer who seeks redemption through joining Mushibugyō. Born into a family of bandits, Shungiku initially tried to avoid a life of crime. However, after his mother was murdered by one of the members of Mushikari, he became enraged and killed everyone in sight until his father's death put an end to his rampage. Later, he discovered that it was actually a member of Mushikari who had been responsible for his mother's murder. Driven by a desire for revenge, Shungiku now seeks out the man responsible for her death.