https://www.puzzlemaster.ca/solutions/1717-3d-string-puzzle-model-y
Ring and rope puzzle. Tons of models of these, though this one apparently has a pretty high difficulty rating
Let us help you identify that mysterious object youโve found.
Currently in CHALLENGE mode: If you've got something obscure knocking about, post a picture, and let's see how we do. Please prefix such posts with "CHALLENGE:" so we know we've got a fighting chance.
https://www.puzzlemaster.ca/solutions/1717-3d-string-puzzle-model-y
Ring and rope puzzle. Tons of models of these, though this one apparently has a pretty high difficulty rating
Knowing these you'll probably have to thread the ring through the slit at least once.
I bet the real trouble will be once you solve it remembering how you did it and getting the ring back on.
Not just the ring, also the disc.
~~Edit: I'm not good at visualising, but it looks like mive the ring to the left over the slit, put the disc through the slit and then move the ring back.~~
Second edit: probably not.

Disentanglement or Tavern Puzzle
Yes, it's a puzzle. The aim is to get the ring off. Had one very similar at home when I grew up.
The trick to knots is that only two kinds of them exist in 2D. The knot that is a knot and the one that isn't. To transform any knot into not a knot you only need to cross the rope through itself once. Ie cut and splice.
If you want I can give you abstract tips. But I think my hint was already close to telling you the solution.
Cut the rope. Got it!

Insanity it is then.
Looks like a topological untangling puzzle.
I've got a similar one, maybe the same puzzle, that's on my desk. I've not figured it out yet.
The rope does not go though the ring. This ring is loose, yes it's a puzzle
They're all variations on this (no spoiler)
you can spoil it. i'm tired of this thing
Usually the "trick" is the fact that the ring fits through the hole.
I am jealous of your tatami mat possession.
:)
I think I will always fondly remember the first time I was living in Japan and I accidentally knocked a salt shaker over, right onto the floor. And I just had no idea how to get a bunch of salt out of a tatami mat. Fortunately, it didn't really matter, because it was salt, and I just left it there.
First one looks kinky ๐
I tangled a puzzle from this line, forgot to fix it, and found it 20 years later. Still haven't untangled it