Онихэй OVA

The OVA will center on Heizou's character, otherwise known as "Oni no Heizou" (Heizou the Demon); the man feared among the thieves and rogues during the Edo Period. A young man traces the stories surrounding Heizou's early days and their "dogs (spies)" from his admirers Kumehachi, Hikujou and Omasa. After hearing from them, the young man heads for Heizou's private residence in Mejirodai and also learns from his wife Hisae. What is the connection between the young man's motive and Heizou?