Hello guys, this is my take on Sans' "blood" thing he has when you hit him in his Genocide fight.

Yeah so this a big problem cuz Monsters don't bleed. There bodies aren't like humans, they turn to dust when they die, they don't bleed then collapse.

So whats my big theory? It's ketchup. Don't worry I'll explain my reasoning.

Sans isn't a Monster Theory

I have seen dozens of people say Monsters can't bleed, so if Sans does, he is simply not a monster. But the thing is his brother is a Monster (He turns to dust right in front of you), which makes people say Sans and Papyrus aren't even related. However, if they WEREN'T related why would Sans say "You dirty brother killer." on a Neutral route when you kill Papyrus?

Oh and in a phone call after a Neutral Route he calls Papyrus "brother" again.

Yeah doesn't make sense if they AREN'T related while Sans calls Papyrus "brother"(His first line about Papyrus he says “now my brother, papyrus…” sorry forgot to put that). Now about the Ketchup theory aswell.

Sans is 'bleeding' ketchup

Now others have said Sans isn't actually bleeding, it's actually ketchup you hit when you hit him, presumibly in his pockets or something. They also point as colors to provce there point more.

Thing is, well Sans is 'bleeding' from the mouth. And again Monsters don't work like humans, anything they eat is instantly turned to energy. So theres no way ketchup and be dripping down his mouth.

So is this just an unanswerable thing with Sans as a whole? Well I have a theory that could explain it.

Hes trying to mess with your Psyche Theory (mine!)

So I propose the simple idea that Sans’ “blood” is in fact ketchup, only there to mess with you to think he’s bleeding, and to make you feel so guilty you’ll either reset and make everything right or leave permanently.

Sans’ entire fight is meant to make you quit or go do everything right. He kills you when you spare him because he knows if you actually want a change of heart, you’ll leave or reset.

Sans stops time at Grillbys. Why is this important? Well I’m saying right after he’s hit, he gets a bottle of ketchup and smears it on his jacked, going as far to put a line down is mouth, then unfreezes time for you to see “blood”. Even if he didn’t have a ketchup bottle on him, he can teleport, I see no reason why the two powers wouldn’t work together in the wacky world of Undertale.

And why doesn’t Sans kill you if he can freeze time? Well he’s aware to the point that we are unstoppable, no matter how many times we die. Will come back. Over and over again. And, again Sans wants you to give up. The second you land a hit on him, he’s already learnt you’ll never change. So he doesn’t give a care anymore. He doesn’t try stopping you anymore due to it being fruitless at that point.

That’s really it for my theory/take thing. This probably has some flaws somewhere, but I feel like it’s a a pretty solid answer to Sans’ blood thing. That’s all bye y’all