New theory just dropped like a nuke

It's a GAME THEORY!

Nope, it would be a game theory if it was posted on youtube by the game theorists (wich i'm planning to find a way to join).
This is a DARTH SANS THEORY!

Look, if you need another proof where undertale comes AFTER deltarune, here is it

This is from an article Waaaaaaay before Chapter 3:
What’s Kris’s plan?
They’re purposely attempting to bring about The Roaring. There are two possible motives for this.
The first: It’s hinted multiple times how much Kris misses their brother, Asriel. When they were little, the game explains, they’d play “Dungeons and Dragons”-like games not dissimilar from the experiences the Dark Realm worlds bring. So there is a very likely chance that these Dark Realm experiences are simply taking place in the characters’ minds, and Kris attempting to bring The Roaring is simply them not willing to let go of the cherished experiences they used to have with their brother.
In this possibility, Ralsei — an anagram for Asriel — is a manufactured character in Kris’s mind created because they wish to relive those experiences with their brother. It’s why Ralsei looks like Asriel. This also explains why Ralsei doesn’t turn to stone after entering Chapter 2′s Dark Realm world, despite the fact that Darkners of one world can’t exist in another. Ralsei’s simply not a Darkner.

Addition: Maybe Kris is secretly Chara, the result of Gaster’s experimentations with “Determination.”

Hmmm, very interesting, but where is specified that kris and asriel used to play dungeons and dragons?

I’ll get that bit..

I believe “Deltarune” is a prequel to “Undertale.”
If that’s the case, Chara will likely succeed in summoning The Roaring, leaving Lightners to fight the Titans. Not only is “The Roaring actually happens” a plausible final chapter — a role-playing game needs to ramp up the stakes at the end, after all — but it also perfectly sets up the story of “Undertale.”
“Undertale,” in a sense, is the ultimate experiment for Determination. We already know how big of a role player choice plays in that game. Additionally, no Darkners exist in “Undertale” because The Roaring turned them all into stone, something Ralsei explains is a consequence of the event.
So at the end of “Deltarune,” perhaps the universe gets destroyed, and the remaining pieces make up the universe of “Undertale.” This would explain why certain character aspects are different (maybe Undyne loses an eye in The Roaring, for example) while other aspects remain the same (Toriel and her ex-husband Asgore are still broken up; Sans and Toriel still have their pun thing;

That's exactly my theory, but I didn't write that much bc nobody would have read it

Then we are agreed

woah

The first: It’s hinted multiple times how much Kris misses their brother, Asriel. When they were little, the game explains, they’d play “Dungeons and Dragons”-like games not dissimilar from the experiences the Dark Realm worlds bring

WOAH

I always tried to connect Deltarune to Undertale. The only issue would be that most of the monsters don’t live that long. Then again, it may be coincidence that their ancestors look almost exactly like them… Asgore and Toriel, I’m pretty sure would survive that long (boss monsters), but Asriel…

Asriel is the son of two boss monsters, this means he's a boss monster too.
Easy as that

I get that, I mean… how young is he when Chara falls?

Like, 8 yo or smth ig.
I'm really clueless abt this actually

Colonized lmao

Hehehe. I wonder if this is how Undyne will lose her eye?

I DIDN'T NOTICE THAT

Bruh, Undyne wears an eyepatch in Undertale, and she has both eyes in Deltarune

My point exactly

Dayum!