The only story where it makes sense for the ML to kill the FL in past life.They were strangers in their past life. Her family committed treason. And she was the main reason for it, and there is way to reasonably believe she didn't want to? like?? she had claim to the throne. And so Rupert just offed her with her family like every other nobles who would commit treason.
I'LL IMPRISON YOU IN THE ROYAL PALACE... but its because im making a city where its safe for women to live in so wait until then.
I'LL THREATEN YOU WITH YOUR FAMILY... thats because you're also threatening me with your life and its the only way to keep you safe
TAKING MY CLOTHES OFF TO SEDUCE YOU
... Rupert???