Takashi Ishikawa starts as an underboss in the Kai Group, a faction of the larger Oudou Syndicate. When Oudou boss Sakurado Michizo and Kai Group leader Kai Shouzo are assassinated, Ishikawa maneuvers to seize control of the Kai Group, succeeding Kai. This power shift happens amidst violent factional infighting within the Oudou Syndicate. Within the Kai Group, Ishikawa's chief rival is fellow underboss Motomiya Haruki.

Ishikawa develops an obsession with acquiring a mysterious mahjong player known as the Dragon. He believes the Dragon's near-mythical luck can be harnessed to gain power in the criminal underworld, a fixation inherited from his predecessor Kai Shouzo's own unsuccessful attempts to control the Dragon. Ishikawa views possessing the Dragon as essential to securing his authority and expanding the Kai Group's reach, especially against external rivals like Kaitou Takeshi. Kaitou, boss of a Kyoto-based syndicate, aims to exploit the Oudou Syndicate's instability to seize control of Kanto.

Ishikawa's central activities involve attempts to manipulate or coerce the Dragon into serving his interests. His rivalry with Motomiya intensifies as they clash over strategy and dominance within the power vacuum. Ultimately, Ishikawa's relentless pursuit of the Dragon and his drive to dominate the fractured Oudou Syndicate lead to his downfall. His story concludes within the original OVA series, his ambitions unfulfilled and his fate sealed by the consequences of his underworld actions.