It's a very old illustration drawn by ZUN in 2001. It's not any character in particular. You can find more info about it on the Touhou Wiki, in the article "Miscellaneous illustrations by ZUN".
@@nonumberlessuser2152 Idk, maybe?he haven't explain much on his art, he just said I want draw this in this theme & feeling. Basically some experiments, but she kinda looks like Alice in MS Reimu ending feeling