Acid Town, Volume 1

In a city where lawlessness rules, Yuki and his best friend Tetsu attempt to rob the headquarters of the local Seidoukai in order to steal money to pay for Yuki's little brother's hospital bill. The mission is a failure, but piques the interest of mob boss Kazutaka Hyodo. He offers Yuki a deal: come to visit him once a week, and he'll take care of his brother's fees. Yuki accepts this arrangement without question, and so makes his first visit.