Ba Kou operates as chief enforcer and right-hand operative to Chinese mafia figure Lin Haifeng. He executes Lin's objectives using assertive and physically aggressive methods, contrasting sharply with protagonist Tsuyoshi Aiba's non-confrontational nature. Ba Kou actively drives Lin's scheme to seize majority stock control of a Tokyo waterfront development company, aiming to transform the area into a criminal gateway dubbed "New Hong Kong."

He engages Aiba directly in financial warfare, most notably during an extended sequence where both compete to acquire escalating shares of the waterfront company's stock. This confrontation unfolds through intense symbolic imagery representing their monetary battle. Ba Kou also employs physical intimidation and violence beyond financial tactics.

During Aiba's investigative trip to Hong Kong, Ba Kou ambushes him, initiating a tense pursuit through a warehouse district that forces Aiba into hiding to evade capture. This encounter highlights Ba Kou's persistent, hands-on approach to eliminating threats to Lin's plans. His demeanor is cunning and unpredictably volatile, often marked by overt hostility. His actions consistently advance Lin Haifeng's agenda, showing no independent motivations or personal backstory.

Ba Kou shows no significant evolution, remaining an unwavering, loyal enforcer. His presence primarily creates physical and strategic obstacles for Aiba, culminating in his involvement in the climactic push to secure stock dominance for the waterfront takeover.