Song title: その魂、雪華の如く (You'll often see it also referred to as "Oath of Soul") Artist (group): SOUND-HOLIC Vocals: A~YA Lyrics: GUCCI Arrangement: panoman PV: yama_ko
As Xbrain mentioned, this PV was one of the flash videos included in the Mesopota Touhou Golden that was sold at C76.
You can find the song itself on SOUNDHOLIC's album "妖 -AYAKASHI-" It's track number 9.