This is Remilia Scarlet's theme from the fanmade Touhou game published by danmaq, Touhou Mutsuigeki ~ Concealed the Conclusion
Original: U.N.オーエンは彼女なのか？ ／ U.N. Owen was Her?
(Flandre Scarlet's theme, from 東方紅魔郷 ～ the Embodiment of Scarlet Devil)
The gloves are off now. It's the final stand-off with the Scarlet Devil. Who will win?
(Psst, you guys... Marisa wins. Sorry, spoilers.)