during one of their "missions", they take on thugs and kuro ends up beating up three yakuza gang members who are menacing a street gangster friend of his. the yakuza work for snake (蛇), the head of a corporation called "kiddy kastle". snake plans to tear down and rebuild takaramachi as a theme park to fit his own goals and dreams. when kuro interferes once too often, yakuza are sent to kill him, but fail. angered, snake then sends the deadly "three assassins" known as dragon, butterfly, and tiger, near-superhuman hitmen, to finish the job.