In a bleak city where gangs hold more authority than the law, Yukio "Yuki" Kousei and his close friend Tetsushi "Tetsu" deal fake drugs in the back alleys to earn some cash. However, with a chronically ill little brother in need of hospitalization, Yuki and Tetsu set their sights on a vault located in the office of the Seidoukai—a well-known yakuza group—in hopes of acquiring a large sum of untraceable money.

Their plan does not pan out, but Yuki catches the interest of the young boss, Kazutaka Hyodo, who promises to take care of his brother's hospital bills and let them go unpunished. But as all deals come with a price, Hyodo tells him to come to his office alone once a week—without fail. With his brother's health as his first priority, Yuki accepts without hesitation and begins to keep his end of the bargain, all while tension brews between Seidoukai and a rising gang thirsty for power.