Titled Onihei ~That Man, Heizo Hasegawa~, the 40-minute OVA prequel will follow a young man interviewing various people about Hasegawa, eventually stumbling onto his personal home and family. Like the series, the OVA will be directed by Miya.
Edo has been suffering from crimes led by Tanbei of Chigashira. Heizou is faced with a mystery when jailed Kumehachi claims that he is not the real Tanbei. Kumehachi remembers Tanbei as a boss who abides by the three articles of a true thief. Heizou took Kumehachi's word and ordered him to find the real Tanbei.
Heizo finds out about the continuous incidents happening at the Kakunosuke Hattori residence and as he heads out, he reunites with Samanosuke Kishii. Hearing that the evil Kakunosuke is scheming a robbery, he surrounds the estate and arrests the clan. But there he finds Ofusa, the first love of both Heizo and Samanosuke...
One night, Heizo gets attacked by a ruffian. Hanshiro Kaneko was searching to avenge his father and became an assassin. His last job was to assassinate Heizo and was set to quit the life of an assassin. Hanshiro attacked Heizo who was visiting the boathouse, however...
Heizo got a visit from Omasa of Nusubito Sake Shop. Now a thief, Omasa left a rough and brutal clan to serve as Heizo's spy. Then Genpachi, a clan member, appears and reports to her that they will carry out the robbery the day after tomorrow and leaves. Omasa follows Genpachi but gets kidnapped on the way...
A burglary occurred at the dry-goods wholesaler where 15 people were slaughtered. It was detected as the doing of Shugoro of Hakabi's clan.Omasa tells Chugo that they can use the mon ey given by her regular customer, not knowing he is in fact Shugoro of Hakabi.
Heizo becomes accompanied by a thief named Zenpachi of Isa. He admired Heizo's ability and character and approached him with the idea to rob the estate of the notorious Ichigoro Masuya. On the day of the burglary, they escape with the cashbox. Zenpachi goes back inside claiming that he dropped the book of "Secret Theft Tactics."
Arson Theft Control struggled to investigate Gohei Ishikawa, a member of a notorious clan led by Shinbei the Viper. As a child, he was abused by his step-father. While Heizo was in Kyoto, the abuse escalated and led to him stabbing his step-father to death. He ran away from Edo and resented Onihei for the incident.
Heizo realized his pipe, a valuable keep-sake of his father, was gone. After patrolling the city, he stepped into a boat where Tomogoro, the boatman was smoking with the very pipe that was stolen. Tomogoro proudly revealed how he stole Heizo's pipe to frustrate the feared "Onihei" of Edo.
Back in the day when young Heizo used to call himself Tetsusaburo, a skilled man named Jyubei Matsuoka entered the Takasugi Dojo during his lessons. Later, Heizo returns home where his father's legal wife, Hatsu, calls him an illegitimate child. Dispirited, Heizo accepts an assignment to rob with his best friend, Samanosuke.
Wasuke of Dojo returns to Asakusa and reunites with Magokichi. His son Isotaro was Wasuke's biological child. But Isotaro took his own life after his boss at Ozuya framed him for a crime. Both Magokichi and his wife Ohiro committed suicide by throwing themselves in the water. To avenge them, Wasuke decides to rob Ozuya...
While Heizo was out, Hisae received a letter which read, "Tomorrow at four, at tea shop Yoshinoya by the Gokokuji gates..." The sender was the man of the past, Kanshiro Kondo. Hisae goes to the place alone. Kanshiro tells her, "don't be surprised when you get back."
Koyanagi saved a woman from throwing herself along with her child in the water. They were the wife and child of Matahachi of Shishidome who was arrested by Koyanagi. Koyanagi was frustrated that he couldn’t catch Monzaburo of Amabata and lets Matahachi out with his family in exchange for information on Monzaburo’s whereabouts.
A robbery at Shop Yamadaya left 17 people dead. From the "Kitsunebi" note left at the scene, it was clear that it was by the Kitsunebi clan. However, its leader has passed and his successor is a former lover of Omasa. As a former member of Kitsunebi, Omasa suspects that they were framed by a criminal.
