Max MacCallister, whose full name is Max O'Donald MacCallister, is a cyborg who once served in the space force before joining a private defense firm that takes on legally ambiguous jobs. He is a tall young man with blonde hair, a black hemispherical monitor for a face that displays only two yellow eyes, and voice heavily processed through electronic filters. He is deeply self-conscious about his mechanical face and secretly saves money to replace it with a more expressive animatronic one, a direct result of his pre-cyborg life as a narcissistic human who feared aging. He was recruited by the military with the promise of a free cyborg operation that would let him avoid growing old, but when he woke up from surgery, he had lost his handsome human face entirely. After his time in the space force, he tried honest work but found himself treated as a machine, never thanked or recognized, which pushed him into cynicism and the gray-area jobs he now does alongside his partner Kurt. His personality is generally indifferent and detached; he shows little interest in others and tends to be money-oriented, often demanding payment for help. However, he also cares about his appearance, frequently fixing his hair, and retains a dry, sarcastic sense of humor. He and Kurt were the only two candidates to pass a company recruitment test and were ordered by their boss to work as a pair, eventually forming a close though largely businesslike friendship. Max handles the technical side of their operations, relying on his exceptional memory, information processing, and hacking skills to disable security systems and operate gadgets. In the story, he is one of six convicts sentenced to clean the interstellar train Milky Subway as community service after being caught smuggling contraband sugar. Initially, he and Kurt refuse to cooperate with the other prisoners, but after Chiharu sincerely thanks them for disabling a security robot, they are moved enough to join the group (though Max still refuses to refund the small fee he charged for the job). Over the course of the train’s runaway crisis, he begins to show cracks in his cold exterior, especially when genuine gratitude is offered, and his past disappointments about being treated as less than human are brought to light during an interrogation. His notable abilities include advanced hacking and gadget operation, which he uses to bypass barriers and disable threats, while his partner Kurt provides the physical power. Max’s development is subtle: the experience of being thanked and of working alongside others toward a common goal gradually reawakens a sense of connection he had lost.