It all started with this dude named ZUN
ZUN likes beer, lolis, beer, magic and beer.
ZUN is good at two things, music and programming.
So he made a game about lolis and magic so he could get money to buy beer. He wasn’t working entirely alone at this point, he was part of a group called Amusement Makers. This game, Highly Responsive to Prayers wasn’t a straight up bullet hell shooter, that started with the next game.
Skip a few games ahead to the sixth game in the series, and my personal favorite, Embodiment of the Scarlet Devil.
ZUN had split from Amusement makers and formed Team Shanghai Alice. Team Shanghai Alice consists of one man, ZUN.
Now ZUN could take all of the money the games made an invest it in beer.
A few of the official games were made with the assistance of other people, had much better art direction, but were 2D fighters instead of bullet hell shooters.
The plots and characterization within the official games is minimal, so the meat of Touhou comes from fan works, from fan games to fan art to the unofficial anime and various manga projects.
Fangames vary from shooters similar in gameplay, to tower defence games to clones of Megaman, Super Mario Bros. and Castlevania. There is even a game similar to Earth Defense Force.
Certainly, Touhou is off-putting to many people. The games are somewhat difficult, a lot of people don’t like the whole every-character-is-a-little-girl thing and the fandom is a bit crazy, but ultimately it’s worth it.
So, help support ZUN’s alcoholism and buy the official games, or not and download them patched in English. I don’t care.