Final answer:
Fans began organizing events focused on specific doujin genres as markets expanded. This took place within culturally vibrant pleasure quarters in Edo period's cities, where townspeople, mainly merchants and artisans, engaged in various forms of entertainment.
Step-by-step explanation:
As markets grew and became massive, fans started organizing events specializing in one doujin genre. In historical context, during the Edo period, centers of popular entertainment developed within special districts, known as pleasure quarters, which were in cities such as Edo, Kyoto, and Osaka. These areas housed activities like theaters, tea houses, bars, and brothels that attracted the chōnin (townspeople), who were primarily comprised of merchants and artisans. Regulation through confinement of such activities allowed for easier taxation and control by the shogunate. The development of these districts played a key role in shaping the cultural landscape and contributing to the creation of organized fandoms around specific genres of entertainment.