Those god forsaken counters.

You can't just say five pencils. You have to say

5 long thin object even-numbers-4-and-under-and-odd-numbers-5-and-over-counter pencil

Go hon enpitsu

The pattern for which is

Pon Hon Bon Hon Hon Pon Hon Pon Hon Pon etc.

They can't simply say the number of clouds the same way they say the number of machine presses. Or count small animals the same way they count apples. Or demigods the same way they count flat objects.

Small round objects and military brigades would obviously be counted the same way though. Obviously.

There's also a unique counter specifically for armed naval vessels and slices of fish on top of balls of rice.

And one just for straw mats.

And one for graves, CPUs, wreaths, and dams.

And while small animals and arthropods have one counter, and large animals have another counter, you count butterflies using the counter for large animals.

Oh and the first 10, 14th, 20th and 24th days of the month essentially have unique names.

I knew a native Japanese guy who spent 4 years mostly away from Japan, and he started to have trouble remembering the days of the month.