Anime I watched as a kid and have been wanting to watch since. Protagonist is a girl who has to fight monsters. The ending has her blood being stolen

I recall when I was younger loving this one anime about a girl who lived in a sweet town, and had a side life where she had to fight monsters attacking her and her school. She also has a master of some sort who encourages her to follow a light she sees in her mind. In the end, it turns out that all her friends and family are monsters of some kind, and that she’s trapped in some sort of nightmare where a villain has her hooked up to something stealing her blood, because it’s precious or something.

Can anyone can help me identify this anime? Always wanted to rewatch it. 🙂 Thanks!