interesting plot, but MC is pretty much looped in as a deterent so the attacking side can really wreck the city. He knows the plan which he was instinctly against staying before the map open, but the flow goes so quickly now he knows everything and all the pieces starts moving and he was the last left to be told what choices he has. That princess pretty much is banking on MC being a good guy and not abandoning everyone to teleport with him and his followers. Its a trade city so if MC actually did abandoning the fight(at least on defense side) it would not bring MCs kingdom any beneficial result, worst would be painting him a coward etc and make the marriage problematic(with Freya).

MC was trying really hard to avoid being involved with the conflict, but now he knows everything thats gonna happen on defending side, all his words and action is gonna affect his and his kingdoms reputation. Thats why he felt exploited at the end. We will see next month maybe I am wrong.

But, yeah, there is some potential for this exchange of political/negociation/military blows that makes this princess join the harem. (MCs digital camera which he brings for teleporting helper would be a massive military advantage in that world with the pegasus army. )