@Hollow7F I was just about to say that the MC seems to not know about that sort of thing, but maybe he's just really really dense? He is a harem MC after all, they can be denser than anything in the known universe.
I love how the demon king got talked down and then talked into doing a proper job, instead of him going on the cliche rampage against the MC which he instantly loses.
Demon King: father doesn't approve of this! No way you're going to marry or bear a child without father's aprroval!
Yuuri: I hate you!
Demon King: Gwah! *suffers critical hit, loses all HP*
And this guy is screwing half the village but still cant tell when a new girl wants to join in?
These girls really must be working hard to keep him blissfully ignorant of everything important.
MC sends a scouting party into the north. Just to scout! Knowing how strict they follow his commands, next year after winter they'll return. "Mission accomplished! Northern nations subjugated!"