There are also Touhou games 1 through 5, but this one is considered the first shmup in the series and as 1-5 are for the pc-98, most people haven't even played them.
I did try them, but they just weren't all that good, the graphics were quite horrible and there wasn't a hint of the awesome music that's found in the later games.
Mystic Square(Touhou 5) was probably the best out of the first 5.
But enough rambling
Embodiment of Scarlet Devil
So this is considered the first and I can easily see why, it's got a lot more polish than the first 5 and it also has a great soundtrack, which the series is known for.
It's also considered one of the hardest in the series.
The game takes place in the mystic oriental land of Gensokyo, as usual. The story revolves around the appearance of a thick red mist, that has covered the land and blocked out the sun. Playing as either Reimu Hakurei (a shrine maiden) or Marisa Kirisame (a playful magician), you must battle your way through 6 difficult stages toward the source of the red mist, and face the "Scarlet Devil" behind it all.
A straightforward story, but no one plays these games for the story anyways, good music and visuals.
I can barely beat it on normal mode, but any touhou player should play this title anyways. Not good for beginners, though.
Also, have a video, if you've never heard of these games, I'll put a few videos in each post.
I'm posting the harder stages and harder difficulties, as those will give you an idea how hard this game can be.
This is the extra stage you unlock when beating the game on normal with no continues used.
And this is the final stage on the hardest difficulty.