I got my favorite character (a handsome knight) in exchange for breaking off my engagement...?
Sonia is a witch who has been reincarnated into the anime "Rasbosu".
She knows that she will be defeated as an evil witch in the future.
Wanting to leave the story, Sonia accepts to break off her engagement to the prince, which leads to her downfall.
In return, she succeeds in acquiring her favorite knight, Ville, as her squire in a previous life.
Last Boss Majo Wa Katabutsu Juusha To Tawamureru Chapter 11
Last Boss Majo Wa Katabutsu Juusha To Tawamureru Chapter 12