This is Shinki's theme from Touhou 5: Mystic Square
As soon as you hear this, you know you're dead.
Shinki, creator and destroyer of her own dimension, Makai. One of the only bosses to actually get frustrated in a fight with Reimu and burn her whole world down from using too much power to get at the heroine. Imagine being Reimu though, only a young teen in her PC-98 days, going up against the god of hell's parallel dimension who's seriously trying her hardest to kill you. I'm not kidding, if you were up against Devil's Recitation... and I thought Byakuren, the kind, loving Youkai Christ was scary using it. However, she was also very beautiful, and I was actually in awe of her. Plus with Emotional Skyscraper blasting through my headphones... breathtaking, really.