The title character is , a historical person who was a Hitsuke Tōzoku Aratamekata Chōkan (Superintendent General of the investigation agency specialized in theft and armed robbery and arson). He started as a chartered libertine before succeeding his father as his heir and being appointed the head of the special police who had jurisdiction over arson-robberies in Edo. Since there was no child between his father and the legitimate wife, he was brought to the Hasegawa family at the age of 17. Heizo was looked down upon by his step-mother saying that he was a child by a concubine. He rebelled against her and ran away from the house. He became the head of "the hoodlums" and led a fast life. His street name was "Honjo no Tetsu" which comes from his childhood name "Tetsusaburō." When his father died, he inherited his birthright and a villain eventually nicknamed him "Onihei," meaning "Heizō the demon,". He led a band of samurai police and cultivated reformed criminals as informants to solve difficult crimes. Later, he was titled "Hitsuke tōzoku aratamekata" (police force for arson and theft), and opened an office at his official residence. While he was called "demon" and was feared, he was forgiving and merciful to those who committed a crime out of necessity or are faithful even if they were criminals. He dedicated himself to establish and maintain the Ishikawajima Ninsoku Yoseba, a vocational training school for criminals, and served concurrently as a Yoseba magistrate for a while.