When I first saw this, I thought it was a vending machine.
I think that is a vending machine also. Coins being slipped and go under the vendor machine is such a common scenario in mangas and stories when vending machines are involved. I can image what a surprise it will be for someone who try to reach the coin blindly.
I think those yus are ko yus lost their adults, by the way. Can't image such a group of adult house yus doing so bad surviving...