The manga centers around Ginjirou Manda, a loan shark business man who is affiliated with many Yakuza gangs in Osaka. He charges an interest rate called toichi — 10% more interest every 10 days, or 365% every year. Thanks to his unrelenting money-collecting tactics, he is feared as "Minami no Oni" or the "Demon" of Osaka's Minami business district. Even when his borrowers tries to scam him, he always finds a way to make them pay his money back. (Source: Anime News Network)

A failed detective takes down vicious criminals!! A new era of outlaw detective entertainment!! Inspector Jirouchou Kiyomizu, a member of the “Give It a Try Division” at the Minami Police Station, is a failed detective, an off-the-charts sadistic cop! In recent years, violent crime has been spiraling out of control! Unable to handle the situation, the police resort to an outrageous, unconventional strategy! To eliminate the poison of criminals, they’ve decided on a grand strategy: to use the deadly poison of convicts!! Under orders from Ochou, the beautiful Superintendent who runs the division, Jirouchou grants parole to the legendary yakuza, Oumasa Rikidou, from Hell Island, the only remaining penal colony in the modern world!! The two, now partners, head out to investigate Osaka’s Minami district, commonly known as Ebishita, where underworld part-time jobs are rampant!! *“With a potent poison!! We’ll put an end to crime!!!!”* (Source: Nihon Bungeisha, translated)

Volume 1 was authored by MATSUDA Yasushi. Volumes 2 & 3 was authored by KYONO Ichiro.