When yukkuri uses logic/explanations that make absolutely no sense to humans
Example: A lot of koyukkuri thinks that showing off the act shitting is pleasant to look at, to the point of them loudly announcing their shitting and asking for anyone nearby to look at them. Obviously, this doesn't make any sense to a human.
Yukkuri logic is often related to the delusional or dumbass tag. But not always, as there are cases where yukkuri logic is simply a yukkuri behavior/tradition that a human can't relate to (such as the aforementioned shitting koyukkuri example)