It's so big, it's held two times a year rather than just annually. It is held at the biggest convention facility in Japan, Tokyo Big Sight. And it is basically one big Artist's Alley, where people sell their self-published manga and art. What is it? Comic Market, or what most people call Comiket. And it is the biggest manga fan event in the world. 2016's Summer Comiket, the 90th, took place August 12-14. Comiket 91 will take place December 29-31, 2017.