Guardian Two is an autonomous robotic killer submarine designed by Nankatsu for war and deep-sea, extreme depth combat. Its sole purpose of operation - its primary function - was to chase down and destroy Guardian One, with which it played war games as Nankatsu perfected its submersibles.
Guardian Two is armed with multiple torpedo tubes and other advanced sensors and weapons capabilities, and is controlled by an advanced AI system.
It eventually was able to destroy Guardian One.