@Kuraiaku, yes the prince is the ml, but the reasoning is actually very sound as to why he did what he did.
I don't want to say too much as it'll basically reveal the whole plot, but he is very much redeemable.
Also, please keep in mind that they did not know each other and had no prior contact before her death, making them virtually strangers, so they can very much start anew. And please remember that she asked to be killed after her family died.
P. S.
As a little spoiler, her family isn't as innocent as they portray themselves to be and what they'll do will hurt the fl more than anything the prince did in the beginning.