Tokitsugu is a machina doll crafted by the Professor to house a human soul. This soul belonged to Mahoroba Village's blacksmith after his physical body perished. The Professor preserved the soul using a mechanical device, transferring it into the machina form. This resulted in a diminutive, doll-like body standing 95 centimeters tall, a stark contrast to his claimed former identity as a handsome human.

Despite his small and outwardly cute form, he embodies unwavering heroism and bravery. He acts as a mentor and older brother figure to other Slayers, with none matching his expertise in rifle combat. His personality is pragmatic and forthright; he avoids dwelling on his non-human condition. He feels gratitude toward the Professor for preserving his soul but remains cautious due to her unpredictable nature.

He possesses a strong disdain for arrogance, frequently leading to clashes with individuals like Homura. In a leadership role, he guides the amnesiac protagonist who emerged near Mahoroba Village a decade after the Awakening, aiding the Professor's investigations into the world's state. His narrative functions include mediating village tensions and undertaking missions against demonic threats.

For broader franchise appearances, his inclusion necessitated consultation with the original developers to maintain character integrity during action design revisions. This cross-media portrayal faithfully retains his core traits: his heroic demeanor, mechanical nature, and mentor role despite his physical limitations.