I've been Proposed to by a Villain

After transmigrating into a novel, Regina Blois is certain of one fact: she is destined to die at the hands of the crazed duke Arsene Graroy after witnessing him murder a political enemy of the empire. And it seems history is doomed to repeat itself as she, despite her best efforts, witnesses the murder again! Duke Arsene has every reason to kill her. So why is he instead proposing??