Do you think it would be cheap if it's revealed that the monsters slaughtered in the video game of chapter 3 of Deltarune turned out to be living beings in a later chapter?
Apparently in the code, the sprites within it are denoted with "sword_route" similar to "weird_route". This lead me to theory that the game is meant to be a manual on the ways to fight against the prophecy. The weird route for board 2 where Noelle becomes stronger by freezing Darkners, and a route where Kris becomes stronger by killing monsters that seem to be hiding from them in the shelter in board 3.
Kris gets caught in a slippery slope by allowing themselves to kill things they don't see as sentient (slain counter appearing in chapter 4 if you beat the Titan Spawn with violence instead of pacifying them, Ralsei views the Titans as beings they must fight since they can't be reasoned with), raising their LV, and becoming more easily controlled. Whereas against Darkners they always held back so they wouldn't kill them even if they fought with violence.
Kris fighting so hard to protect their friends from being manipulated by the Soul, believing they can counteract its influence, only to realize they'd fallen into a trap. It sounds pretty sick as a route. And during their finak fight with Tenna, if you played the video game, Kris is indicated to act aggressively towards Tenna in dialogue, so this might be showing the start of the fall on their own sword.
However, going back to my original point, do you think it'd be cheap if it was revealed the monsters in the video game were actual living beings?
To me, I took the game as something left for us by someone (likely Gaster) to show us ways to go against the prophecy. I never saw killing the things within it as killing living beings, but apparently the game records a kill count in the code if you do the game. And that has me worried we might be later judged for doing that, a la Sans in Judgment Hall.
I was fine with that in Undertale, because if you listen to the game, it's pretty easy to avoid being judged negatively if you just listen to what the game asks of you. Whereas here, it doesn't feel clear at all. I feel like it's going to suck if it's revealed in chapter 5 or 6, years down the line, that they were living beings, and you unintentionally committed a genocide, and have to redo parts of the game.
And I think the thing that really turns me off such an idea is what about the arcade machine that blows up in chapter 2?
Why wouldn't you just view it as a game within a game like that?
Yeah, revealing years down the line that playing the videogame-within-the-game is actually going to mess up a "pacifist" route does feel like a cheap gotcha to me. Especially since playing the videogame is (near?)required in order to fight the secret boss of Chapter 3, when all the other bosses are fine to do (even advantageous to do) on a normal playthrough.
As much as Undertale/Deltarune like to mess with players' expectations, that feels pointlessly frustrating. It wouldn't say anything interesting thematically because (as you say), the intentions are confusing at best. A bunch of players who put time into defeating the Roaring Knight would redo their saves and skip that boss to be on the route they were intending, but afterwards everyone would just avoid interfacing with the game-within-the-game at all.
I think a Kris-like character being lulled into killing beings they didn't realize were sentient could work in another game… but in the broader context of Deltarune, I don't see the point. Kris is already a very morally ambiguous figure, at times seemingly antagonistic to the Red SOUL, which made a lot of people think they were evil from Chapter 1! And the Weird Route already exists as the true "slippery slope into horror"-type story. So what would such a "Kris becomes evil because they murdered videogame people" route add that is different?
I do think the game-within-the-game is meant as a manual. But the theory I'm more inclined to subscribe to is that the "sword_route" is wholly a guide for the Weird Route, foreshadowing future chapters for it while also acting as an in-game hint for people who play Deltarune without looking up online guides. (And which I'm very happy exists, because the starting conditions for the Weird Route are so much more obscure than Undertale's comparable "secret bad ending". Being forced to look up fandom discussions to even realize an alternate route exists isn't great gameplay.)
If anything, I think it's more likely that those internal counters might eventually be relevant on the Weird Route, precisely because that's the "all bets are off, you need to do bizarre and un-telegraphed stuff in order to progress this" route. Maybe you do need to be as violent as possible in all situations for some later Chapter 5-6 condition, who knows. But at least that would feel less out-of-left-field.
…Or those counters could just do nothing, of course. Something something you can't change the ending. Or, for that matter, maybe Susie will be impressed by your cool skills later in another videogame if you played the game in Chapter 3.
We really can't say yet! So it's not something I'm worried about.
