Things were going so well. Assassinated by a brigand on the road. Dammit. Knew I shouldn't go to that stupid birthday party.

I feel like that was pretty good for a first try!

OK, I've played it through several times now.

I have to say, as much fun as it was the first time, each time through gets less so. It's the exact same thing over and over, and quite frankly, I cannot figure out how to survive the final confrontation. Being 100% at all military strategy still loses, being 100% at all Lumen still loses... what do I have to do here?

And I'm sick of the exact same events in the exact same order.

I'm guessing there is one and only one way to play through this and win, and that's boring. :(

In the final duel - beside the Lumen skills - you need either Swords or Decoration (!) skill to win.

Though I only completed the game once, but I learned that there is a non-Lumen path as well. You're going to need the press, the hospital and every other military achievement and - if you also have masterful strategy - you can beat the enemy fleet before it reaches the shore. (So you don't have to duel the evil king.)

It's also possible to have him show up at your palace but avoid the duel in at least three different ways, depending on your skills and prior decisions.

Mnope. I played a "pretty pink magicless Disney princess" Elodie and won the war with the power of music and good intentions, while others did it with a "Elody the witchqueen of blood" playthrough, so there are definitely several ways to win. The endings are collectible items, just like the "death chibis". They are difficult to find, though, and you will probably need savescumming a few weeks back to try different skill sets that will allow you to get through the gauntlet of the war to the ending you're after.
And although the moment any event will happen is fixed, many of them will or will not happen according to your previous choices and skill tests.

I agree the replay value drops after a few playthroughs, but the "decision tree" is quite dense, with hidden branches.

And your first death was exactly the same as mine. That birthday party is for me the moment where things get really dangerous ^^

Well, I'm not done with it. I'll keep trying. I think when it's all said and done I will have had my few bucks' worth!

Finally got a bloody win, ha ha! Master Lumen + sword + athletics.

Looks like there are quite a lot of medals left. Should be fun to eventually unlock them all.