Doctor T, originally known as Dr. Tokioka, is the scientist responsible for the necrolization that brought Brandon Heat back as the deadman known as Beyond the Grave. His surname is Tokioka, but his given name is never revealed. In his past, he worked as a researcher in a laboratory owned by the Millennion organization. This lab was attacked by a violent criminal named Mad Dog Ladd, who killed all of Tokioka's colleagues and took both the scientist and his research files hostage.

Later, he was among the scientists forced to demonstrate the results of necrolization to Millennion members Blood War and Cannon Vulcan, watching grimly as they prepared human subjects for the process. Following this period, he was coerced into continuing his necrolization research under the orders of Harry McDowell. It was during this time that he played his most pivotal role, using the corpse of the murdered Brandon Heat to create the deadman Beyond the Grave.

Dr. T is not the stereotypical mad scientist driven by a thirst for knowledge. He is a pensive and remorseful old man, haunted by profound guilt over his role in creating the necrolization technology. He views his work as an irredeemable sin and his own compliance as an act of cowardice that damned Brandon to an unnatural existence. This guilt is so consuming that he eventually rejects his own name, Tokioka, feeling unworthy of it. He begins calling himself Dr. T instead, a symbolic act of self-punishment for the crimes he believes he has committed. Beneath this burden, he retains a genuine streak of kindness and becomes a dedicated caretaker and ally.

His primary motivation is one of atonement. Dr. T decides to use his forbidden science against those who would exploit it, believing that Brandon as Beyond the Grave is the only one who can stop Harry McDowell's tyrannical plans and his army of deadmen. He aims to counter the destructive potential of necrolization by creating an even stronger deadman free from the control of others. His role in the story is that of a mission controller, technician, and sole confidant to Grave. He operates from a hidden base, which can be either an armored truck or a secret laboratory, that contains the essential life-support systems required to sustain Grave's decaying body. He is responsible for Grave's periodic blood replacements, maintaining his weapons, and providing tactical information on where to strike against Millennion.

His key relationships are defined by duty and regret. He serves as the caretaker for Beyond the Grave, a role that mixes scientific obligation with a personal mission to support the man he unwillingly resurrected. He is also the protector and guardian of Mika Asagi, keeping her safe while she is a child and later watching over her. He maintains a connection to the old Millennion through his twin brother, who served as Big Daddy's butler; it was through this brother that Dr. T was able to deliver a final letter from Brandon to Big Daddy, an act that resulted in the grieving crime boss punching Dr. T in anger.

Throughout the narrative, Dr. T undergoes a clear development from a coerced, haunted researcher into a proactive agent of redemption, fully committing to helping Grave dismantle Millennion. His most notable abilities are his genius-level intellect and his expertise in the field of necrolization. He is able to revive and sustain a corpse as a functional, powerful agent. He also demonstrates considerable ingenuity by developing specialized anti-Superior bullets, which are crucial for defeating the enhanced lieutenants in Harry's organization. In the anime, his story ends with a heroic sacrifice; during a battle, he shields Mika from an attack and sustains a mortal wound. Using his last moments, he transfers his own blood to containers to sustain Grave for an extra ten days before finally succumbing to his injuries.