What is Touhou?
Officially, the Touhou Project (henceforth Touhou) is a long-lasting series of PC games, with the first game being released in 1996 and continuing to the present day. Touhou is most well known for its so-called danmaku games; one can think of these as much more creative, challenging, and aesthetically beautiful versions of the classic arcade game Space Invaders. The video below showcases gameplay on the hardest difficulty of the most recent danmaku game in the series, Touhou 15 - Legacy of Lunatic Kingdom. The main concept of the games is quite simple—just dodge the bullets—but in actuality the variety of difficulties and bullet patterns make the games enjoyably replayable for hours on end, as one attempts to clear the game. For example, achieving the impressive skill of the player in the video below is certainly not possible without countless hours of practice.
The official Touhou games are created by the misleadingly named "Team Shanghai Alice," which has only ever consisted of just a single developer, Junya Ota, who goes by the moniker ZUN. He does all of the game design, composes all of the music, and writes all of the code by himself. To date, he has released a whopping 24 games in the Touhou series alone. Games with integer numbers, like Touhou 15, are danmaku games, but ZUN also releases games with non-integer numbers like Touhou 14.5 - Urban Legend in Limbo, a Street Fighter-style fighting game, shown below.
Lorewise, the games generally follow the shrine maiden Reimu Hakurei and the kleptomaniac witch Marisa Kirisame in their adventures around the mythical world of Gensokyo. Over the years, ZUN has built up quite an extensive world, with a constant focus on character development. The interested reader can explore the lore of Gensokyo further on sites like this wiki.
The Touhou Fandom
Touhou is much more than just an official series of games, however. ZUN has an extremely lax policy on derivative works, which puts almost no practical restrictions on what doujinshi creators can do with elements of Touhou. Perhaps partly as a consequence of this policy, much of the material related to Touhou nowadays is actually fanmade, a phenomenon which seems unique to a few popular Japanese game franchises. In fact, a cursory Google Image search for "Touhou" turns up not official art, nor screenshots of gameplay, but almost exclusively fan art. Fan art is also by far the most common topic on the Touhou forum section of 2channel as well as on the Touhou subsection of Reddit. Such fan art often exhibits much greater attention to detail than ZUN's official art; after all, ZUN is just a single person, however hardworking he may be. A couple of well-drawn examples are shown below, followed by a collage of the franchise's official art for comparison.
Comiket, the largest doujinshi (roughly, independent fan creations) convention in the world, serves as another testament to the popularity of Touhou among doujin creators. At Comiket, Touhou is routinely one of the top three franchises by representation. For instance, Touhou-related merchandise and cosplays are both quite common at Comiket, as shown below. It is apparent that ZUN has designed some extremely compelling characters over the course of developing the lore behind Touhou, drawing the interest of scores of doujinshi creators.
It is clear that somehow—whether due to people enjoying the gameplay, loving the character design, or wanting to take advantage of ZUN's lax policy on derivative works to create doujinshi--Touhou has amassed a large, dedicated, and actively contributing fanbase. As I argue in this project, this fanbase has played a significant role in increasing the reach of the Touhou franchise to new fans, especially overseas. In particular, I will focus on the extensive communities dedicated to remixing official Touhou music, making unofficial Touhou-themed games (henceforth fan games), and providing translations into foreign languages from the original Japanese. However, these of course do not nearly comprise the entirety of the Touhou fandom.