Pure, Concentrated, Delatrune Crack-posting:
Now I've been thinking about this for a while:
HUMANS EXIST IN DELTARUNE! AND LIKE THERE'S MORE THAN ONE HUMAN!
YOU know what that means? Human culture exists in Deltarune.
How do we know this?
Well we see Kris, an explicit Human, as refered to by both the game description and several in-game characters, as compared to the Mnsters. This is actually really important because from the Monsters' perspective, why wouldn't Humans just be a weird type of Monster? After all, monsters range over humanoid mammals, birds, reptiles, fish, living skeletons, and literal elements--and all of them consider themselves as explicit non-Human Monsters--so why aren't Humans just some odd hairless-ape Monster. Now we only have two explicitly confirmed differences between the two--Humans have significant souls and Monsters lack them, and after death Humans become corpses while Monsters turn into the dust. However, these differences are not obvious in common-life--people don't spend their days at funerals and Kris ripping out their soul is heavily implied to be unusual behaviour.
The clear ethnic distinctions between the two groups imply two things:
1. The total Human population is at-least somewhat similar to the monster population: If Humans were significantly outnumbered by Monsters, their differences would be overlooked and they would be hairless-ape monsters.
2. This also implies they have their own distinct culture. Their large population, seemingly rarely-seen amongst Monsters, implies they live in their own settlements, while their clear distinction from Monsters, with some Monsters being speciest, clearly implies this.
Now we basically have no clue about Human culture except that its probably different to Monster culture to some extent, so this will be the source for the following headcanons:
TO BE CONTINUED.