Its not 100% ketchup, its not sweet and sour sauce or duck sauce (i dont think... never had duck sauce). It just tastes like sweet and tangy, kinda spicy ketchup (but not at ALL like cocktail sauce). its red like ketchup, has the texture of it too. But I'm pretty sure it's not just ketchup.
Anyone know how to make it?
I tried mixing some ketchup with soy sauce, some sugar and hot chili sauce, but that was definitely not it.
Thanks for all the suggestions! I believe that the recipe for Tonkatsu sauce that yamiko posted is close to what I was looking for!