This is why Oboro is best girl. That's the most reasonable and sensible plan to make everyone happy.
Plus with such a centralized power in Yuragi Inn, Japan will enjoy a stable and peaceful era... well, until Kogarashi's descendants start fighting amongst themselves.
The harem train will not be stopped. Those not on board when the train departs will be left behind. Yes even Hibari.
Perhaps in a future chapter Kogarashi learns to make spirit body projections of himself. Even if existing temporarily, he can service more women at once. Umm... I mean fight more bad guys at once. Yeah that's it.
Don't give up, Oboro-sama, you got DA PLAN! Yuuna's on board & just a few judicious hints to Chisaki will sway her to your side. With the two chief waifus in agreement, all the others will eventually crack & buckle under to the new regime.
You know Oboro really makes a good point here, when Genshuro was trying to make Yuuna his wife he did say he was going to make the other girls be in his harem, so if Fuyuzora is the only Yatahagane left wouldn't that make him a special case and let him take multiple wifes so he could make the clan bigger?
That's not a bad idea. You literally kill like 4 birds with one stone. I honestly can't see no better ending than that. But it really all boils down to kogarashi himself.
I'm on board with this plan/idea but author addressing it and shutting the idea down in a funny way might have been a clue from author for what future holds and kind of a sad flag for us.
Oboro you damned trash-monkey... It is one thing you tacitly accepting Worst Girl pairing off with the protag as though it were natural for the most boring, generic, token normal girl to win.... but you'd better not end up roping Nonko-chan and Yaya-chan into your harem plan! Ugh... might have to demote you back to Worst Girl again. Filth!