What to do if you're forced to marry a demon king's daughter in a horror game?

Is there anything more unfortunate than being caught up in a horror game? Yes! Becoming a 1.5-meter-tall, silver-haired little girl! So, is there anything more unfortunate than becoming a little girl?
Yes! I'm being forced into marriage by the world's strongest demon king! Now, all these unlucky things have happened to me, what should I do?