Born as Ryusei Chisato, he was the offspring of two scientists with nearly supernatural intelligence. His parents were murdered, but he was saved by his companion, the shapeshifter Garo. Raised by his foster parents, the Kaguras, Tatsuo dedicated his life to finding his parents' murderer to exact revenge. He uncovered that his grandfather, Kogetsu Chisato, was responsible for his parents' deaths. Chisato then set fire to his mansion, intending to kill himself, Tatsuo, and Tatsuo's sister Maya.
Tatsuo survived and continues his battle against crime and corruption.
