I’ve heard multiple times that it’s not okay to allow any food to go down the drain even with a garbage disposal, I guess because solids shouldn’t go down the drain. But we put a shit ton of solids down the drain through the toilet and that seems to be fine. Does the toilet go to a different sewage pipe then the sink? Or does shit have different properties that make it dissolve better?
It’s not unique to Japan/Korea, you can definitely get it in the US. Fryaway is at least one brand of it, but I’d be shocked if you couldn’t get others.