B't Max is a massive mechanical entity whose design draws from the Black Tortoise, known as Genbu in Japanese mythology and Xuanwu in Chinese tradition. As a B't, a type of mechanical life form, Max primarily dwells underground, where her internal laboratory serves as the operational base and primary transport for her human partner, the Spirit General Hokuto. Her physical form is colossal, and her outer armor possesses exceptional durability, being impervious to attacks such as underground missiles, which has led to her being recognized as possessing the strongest defensive capabilities within the Machine Empire.

In terms of personality, Max exhibits a serious and perceptive nature, coupled with considerable emotional depth. Her most defining trait is her unwavering loyalty to Hokuto, to whom she is deeply devoted, though she also interacts willingly and effectively with other characters when necessary. Max functions less as a frontline combatant and more as a mobile fortress, a guardian, and a crucial support facility. Her internal laboratory, where Hokuto conducts his experiments, makes her indispensable to the protagonists' cause. The most significant demonstration of her role occurs when she and Hokuto rescue the heavily damaged B't X and his partner Teppei Takamiya. Within Max's laboratory, Hokuto is able to revive X and perform a critical power upgrade, transforming him into Neo B't X, which is essential for the battles to come. Her capabilities and facilities prove crucial for the protagonists' objectives throughout the narrative.

Key relationships define Max's place in the story. Her bond with Hokuto is the most central, with their shared history and his personal motivations for joining the Machine Empire informing their deep operational synergy. Revelations about Hokuto's past only serve to strengthen the connection between donor and B't. Max also develops a significant, albeit less direct, relationship with Teppei and his B't X, acting as a safe haven and a source of reconstruction for the injured warrior. During the events of B't X Neo, Max joins the journey to the Machine Empire's central tower, engaging in the culminating confrontations and contributing her defensive strengths against the ultimate threats, including the apocalyptic B't Rafaello.

Max's development throughout the series sees her transform from a hidden fortress into an active participant in the final battle. In a climactic act of sacrifice, Max and Hokuto unite with their allies, channeling energy from a solar capsule to stop a global catastrophe. Their self-destruction in this effort underscores the narrative's themes of sacrifice and legacy, as they dissolve together to avert worldwide annihilation. Her notable abilities extend beyond her defensive power. Max can generate a Protective Shield, an energy layer that repels surrounding enemies. She possesses enhanced sensory perception superior to other B't, allowing her to detect subtle threats. Her systems also include a sophisticated computer capable of performing detailed analyses on the human body, which Hokuto uses to diagnose his own illness. Furthermore, her head unit can transform into an autonomous vehicle called the Scramble Cruiser, which Hokuto utilizes in the manga's final sequence.