I think we have three possibilities (spoilers!):
First of all, yes, maybe we will have to choose only one favorite man. And yes that will be awful cos they all are so cute, it definetly will be heart-breaking.
Another option that we will not have to choose and game will end on our wedding with Bernard. At list three characters already teased us about that so it quite possible.
But there is another thing and it's little bit anxious. After Gunnar's death I'm starting to think that MC might die. Maybe to save someone, like sacrifice for the greater good. Also we still didn't know a thing about MC, where (s)he came from, how (s)he became an apprentice, why all this demonic persons are so interested in him(her) and that kind of stuff. Maybe we will never know cos it isn't important, but who knows.
But in the end it is a story that Hyao telling. I think he already know the answer and we can just listen what he wanna say to us. It doesn't really matter what we think about it, so just relax and enjoy the adventure :з