This is after Tessa got sucked into the portal in the creation and destroyer the beginning and the end book. She was saved by N,Cyn and Ema
After a while Tessa replaced her arm that was gone (again read the top of the description that's the title of my first murder drone au) she replaces it with an robotic arm (oh and if you're to lazy to look for what happened to her then a Cyn named M,Cyn cut of her arm) 1 year have passed and she knows how to use her new arm pretty well. But Tessa touched something she was not supposed to some of her organs turned into mechanisms and if you want to know what it's looks like check Tessa bio,
Edit:I didn't see Tessa as a main character Uzi was still going to be the main character but since we're mainly focusing on Tessa I guess she is.
If you get this to 1000 reads then I'll make a remake of this.