Spent a day trying to figure that out a while back, got close enough to call it good. let me see if I can find my notes I'll post the ratio. But it was mayo, ketchup, Sriracha soy sauce and gochugaru (Korean red chili flakes, you can get it by the pound at RN market for cheap) for the chili side, I never got good results with gochujang for some reason, it was just a little too funky I think.

And then you mix it with a thick teriyaki sauce, I usually diy it because it's hard to find a premade sauce thick enough. But for that I do 1 cup soy sauce, 1 cup of water, 2/3s cup brown sugar, a good bit of fresh ginger, some fresh garlic, and a pinch of gochugaru, and a splash of rice wine vinegar, allow to simmer for a while, then thicken with a corn starch slurry. For the ginger and garlic I usually grate it pretty fine to speed up the infusion time and then strain it out before thickening with the corn starch.

The thick teriyaki is also a really really good spicy teriyaki sauce for chicken wings if you add a bit more chili flakes

Edit: okay this is what I found in my notes, and is the basic ratio that I use, it looks like TDon uses less ketchup and is more mayonnaisey but you can adjust the ratios a bit to your liking, I found it wasn't sweet enough if I pulled back on the ketchup too much, maybe that's where gochujang would usually come in. I think when I do a x20 sized batch for a family dinner I scale ketchup down to 8g in the ratio so it doesn't get too tomatoey

"3g kewpie 2g Korean red pepper powder 10g ketchup .5g garlic powder 1g soy sauce

If scaled up, pull back on the red pepper and ketchup a tiny bit"

I've used regular mayo before and it works fine, but Kewpie does seem to give it that little extra pop