Melissa Mao and her team are summoned by MITHRIL to probe an Arm Slave of unknown origin that surfaces near mainland China in the Taiwan Strait. The group sets out to Hong Kong, a city divided, in search of the mastermind behind the enigmatic mech. As they delve deeper into the case, suspicions arise that a failed SRT applicant who underwent training in Belize alongside Sousuke may be responsible for the creation of the Arm Slave.