Their petardo

Newborn sage fawn gets kidnapped and dropped onto the doorstep of a man. However he isn't you average man. He owns one of the most prestigious assassin training programs in the world. Sage lives with the torture for 9 years until suddenly one day she snapped but her tragic upbringing didn't end their because once she escapes she falls into the hands of the enemy where she learnt things no other would be able to teach

Now at 15 she is a complete badass. But what happens when some unexpected guest become apparent in her life.

Who is the enemy?
Who's enemy was it?
Who are the unexpected guest?

Found out in 'their petardo'