【東方ボーカル】Flames Within These Black Feathers - Foreground Eclipse 【Subbed】

【Original】
業火マントル (Hellfire Mantle) / Stage 6 Theme
霊知の太陽信仰　～　Nuclear Fusion (Solar Sect of Mystic Wisdom ~ Nuclear Fusion) / Reiuji Utsuho theme

【Game】
東方地霊殿 ~ Subterranean Animism (Touhou Chireiden ~ Subterranean Animism)

【Credits】
Arrangement: Suzuori ／ Vocals: Merami, Teto ／ Lyrics: Suzuori, Teto
Doujin Circle: Foreground Eclipse ／ http://www.fg-eclipse.net/
Album: Tears Will Become Melodies Tonight ／ 2010-12-30 (Comiket 79)

English Translation: Kafka-fuura / http://kafkafuura.wordpress.com/
Illustration: ついじ@Pixiv

Yes this was in fact one of the songs used the in Reimu vs Utsuho Dog Fight video.

There are also two different versions of this song; one with screamo and one without.