The Idea of us (Karmagisa)

Hi everyone, this is my first book so please go easy on me (I'm trying, but I'm open to feedback) if anything in this book doesn't make sense or you see a mistake my messages are open

What happens when everyone you ever loved was taken away, and the only person you know that's left, is one of the world's biggest criminals and is one every wanted list to exist, teaches you how to be just like them, to get your revenge

When Nagisa is sent on a mission to a high school with her partner, to kill the fastest being on the Earth that cannot be known to the public, because of its nature, what will happen when she runs into a certain red head, we all know and love who is to curious for his own good.
And someone she thought she'd never see again comes back to haunt her

Friends will be made and betrayed
Love and lust are bound to be broken
and all for her sake of 'revenge'
Will she be able to defeat the demons, or will she go down trying?

Disclaimer- I don't own any of the characters