Quack is a substance associated with an underground smuggling operation primarily involving opium. Kaeru Haya, a ronin watch leader, asserts that the operation deprives Lord Miya Tetsuya of customs revenue. Quack is characterized as a smuggled substance specifically evading customs duties.
The smuggling operation has been ongoing, requiring significant coordination among various parties, including the ronin and potential connections to a Mantis ship in the harbor. The implications of Quack's smuggling illustrate the corruption and illicit trade impacting the local economy and law enforcement.