Hatsune Miku - Dark Behind These Exalted Words (甲斐甲斐しい言葉の闇に) by TadanoCo
"Of an anarchy-ridden heart and the profound darkness." It's been a while. Enable CC for romaji and (slightly singable) translation!
Romaji Title: Kaigaishii Kotoba no Yami ni
Music & Words & Art: TadanoCo (ただのCo)
http://www.nicovideo.jp/mylist/35809941
Official mp3 download: http://piapro.jp/t/1auq
Reprinted from Nico Nico Douga: http://www.nicovideo.jp/watch/sm30290484
TadanoCo uploaded on Christmas, so wrong holiday.