So I've been thinking a lot about the recent Asgore developments in Chapter 5, and what they could possibly be alluding to. Asgore says he wants to prove that Dark Worlds are real, and they could be the result of an incident from a long time ago. 

Now admittedly this doesn't have much to do with the theory itself, but it is what spring-boarded my train of thought, so felt it was necessary to start, and once again, I'm sure there are PLENTY of holes with this theory, but it felt plausible if you consider everything, and I will wrap back around to Asgore by the end.

It made me think of current circumstances and the parallels they make towards the circumstances in Undertale. In both Undertale and Deltarune, Toriel and Asgore are divorced. In Undertale, we know why they are, because Toriel didn't approve of Asgore killing more humans to take their souls. In Deltarune, we don't know WHY they are divorced, and it could just be simple marital issues, it could very well be, but knowing Tricky Tony, I don't know man it just seems too simple.

We know there IS a history between humans and monsters in the Deltarune universe due to the book in Kris' house written by Gerson (who was IN THE WAR canonically in Undertale) but we don't really get to know what this history is, at least not yet.

Now let's talk about the Undertale 10th Anniversary livestream, specifically a certain character that appears in the footage in Snowdin. In the stream, we see what appears to be a very young version of Noelle. They don't talk to her, they don't even acknowledge her, but she's there. Now what's weird to me about this, is if you wanted to just hide an Undertale counterpart to Noelle and call it a day as a reference that would be one thing, but it's weird that in Undertale she's considerably younger than her Deltarune counterpart, who's a teenager. It's also worth noting that it's believed that an Undertale counterpart to Susie exists as well, due to an NPC in waterfall namedropping her, although the names aren't spelled the same. And Frisk is also a child.

So where am I going with this? Well let's look at our main protagonist Kris. I always found it odd that despite having no correlation, Kris's name is literally Frisk without the "F". Now this could of course just be a simple reference and nothing more, but I think it's fun to think of another possibility. Think back to the Susie and Noelle point I brought up earlier. In Undertale, Noelle, Frisk, and (presumably as we don't actually see her) Susie are all young children, but in Deltarune, everyone in the main cast, including Kris, is a teenager. 

I believe that Deltarune is indeed a sequel to Undertale, and Kris is Frisk aged up as a teenager, now before you grab your torches and pitchforks, let me plead my case lol.

Asgore is trying to prove that Dark Worlds exist, as well as a Dark World that appeared ages ago. Hometown feels....almost too peaceful, like a society where everyone is brainwashed into thinking everything is okay (sort of like Derry from Stephen King's IT if anyone is knowledgeable). What if Deltarune takes place many years after Undertale, and when the first Dark Fountain was created, something within it, or the nature of Dark Worlds, took hold of the town, and made everyone forget what happened and who they truly were?

Another thing this would explain is, we haven't seen Asriel yet. Sure they claim he's at university, but you'd think he would call home, check on his family, say hi to mom, yknow, the normal things College kids do?

And it would explain Toriel and Asgore's divorce in Deltarune, Toriel dislikes Asgore, but she can't exactly remember why.

And that kinda wraps up the theory. Again I know it's not water-tight and there probably are lots of holes, but I thought it would be fun to consider, I'd like to hear you're guys' thoughts! :)

The Amnesia Theory, a theory to connect Undertale to the current lore (I'm aware it has holes but I felt it was something I wanted to bring up)