Protector of Kingdom and his heart

A princess who was shouldered by responsibility of protecting prince from his ill fate and enemy who lives under same roof with him
Without any promise she gave her everything to that one promise and fight with all she had within her.
What is the promise which made her leave everything?
Can she gane the trust of prince or is she really loyal to him or there are other secret which was hidden in the dark?
Who is the person who wants to kill prince and why?
To find out answers to these questions continue reading new chapters.