Remix would be Night of Nights :v
Original: Native Faith
Remix: Usatei
This needs its own thread!
racking my brain to remember but I think mine where
Original: I can't actually remember
Remix: It was a Marasy video for Lunatic Princess. before that I had only heard the random IOSYS Vocal song on youtube every so often. It was watching that Marasy vid that finally made me start hunting down Touhou music.
Vocal: Overdrive, this one I know for sure because I heard it as part of an AMV. Then it was "My Body Wishes that you Burn to the Moon" right after that. It was an AMV by the same dude who did the Overdrive AMV and I watched them both back to back.