What song am I thinking of? [from a video game]?

I can't remember the video game [or the name of the character for one] but I remember that scene from the video game, he is walking up on a roof, and this girl is sitting there. She is ghostly pale,white hair, and has a scythe I think. She is wearing a black frilly/lolita dress. And then as they fight on the roof, a song that SHE sings is playing in the background. Sorry I can't give any more details. Its from a video game a while back though. I'm sorry! But does anyone have an idea what this song is?