The Comic Market (“Comiket”) is an event held in August and December where groups and individuals can exchange and sell self-published comic books known as dojinshi (同人誌). It has its roots back in the 1970s when a growing number of manga fans were frustrated at the lack of diversity among the established publishers and the difficulty new authors faced in trying to get their work seen by a wider audience. In 1975 a small manga reiew club called meikyu (迷宮) or “Labyrinth” decided to self-publish a magazine that reviewed dojinshi and organise events where authors could share their work freely. The first event—the basis of today’s Comic Market—featured 32 “circles” or groups of manga fans and was attended by about 700 people. Today those numbers have increased to 30,000 and half a million, respectively—and Comiket is a major event on the calendar for manga fans throughout the country. The event also gets a good amount of media coverage because many of those attending the event do so in “cosplay” (those wishing to take photographs are requested to kindly ask the person/group for permission beforehand).
The dojinshi area is open from 10am to 4pm each day (the cosplay dressing rooms until 5pm). Entrance to the market is free. You can read more about the market and its history at the official website (multi-language PDFs available for download—here is the English version).