The classic, "pass out after the battle so the author doesn't have to describe the aftermath other than a brief summary," solution.
Mikage would be furious at being left out of the acclaim. Because it's about what makes him look good.
That's a patterned dress.
Politic > personal fame. But he has his own goals, so that's fine.
Straightforward with no excuses, nor accepting any alternate rewards. This is why he's a great protagonist.
Princess is smart to argue the political advantages, since he isn't a nobody to leave alone. She does indeed rock.
It's typical for royalty, unless they're the direct heir, to lose their royal status and noble inheritance rights if they marry a commoner.
King is reasonable. No need to force a solution no one likes.
And here comes the second fiddle.