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)