Well, the first Touhou-related thing I found on the Internet was a U.N. Owen remix. 12 year old me listened to a lot of Pokemon soundfont remixes for whatever reason, and I found this video.
I thought it was pretty good, but I didn't even consider that it might be from anything in particular. I ACTUALLY got into Touhou about 4 years later when I started browsing TVTropes regularly. The name kept popping up there, eventually I read the page, curiosity led me to look up some gameplay videos, and I found MegamanOmega's channel. He recommended downloading the games from the old version of this website. Honestly, it's not the most interesting story.