A high school girl, who's an innocent airhead goes to school at mornings and has a normal life. When night time, she turns into a skilled swords master and fight demons.
But if you keep watching, you notice something is odd. And then the anime turns into something really different and you are left like "...What just happened?"
This way it is pretty entertaining. You wonder what's gonna happen next and keep watching. You can even pull a all nighter since it doesn't have many episodes.
It has gore, nice animated fighting scenes, psychological events, romantic moments, comedy included stuff and so on. So keeps your attention and you don't get bored while watching.
There is one thing I found as a bad point. It may be counted as a spoiler, so read the rest at your own risk.
When Saya isn't herself, she is way too naive. But it doesn't affect her fighting.
She doesn't question anything and she acts so slow.
She repeats "I have to protect everyone" in her head and appearently cares for them but before she actually begins to fight, someone she loves must die in front of her eyes.
Plus, when Saya still hadn't get her memories back, she couldn't save her friends from death but she could still sing her morning songs happily. That didn't really make sense.
Overall, it's a good anime to watch and I totally recommend it.
