It’s funny on multiple levels seeing as how Japan invented the conveyor belt sushi shop.
For the uninitiated, at such conveyor line sushi shops, the chefs place specific color quarter plates on the line, with a couple of pieces of sushi. The conveyor belt line winds around the establishment, and at any time the customer—who is eating directly behind the conveyor, can pull off a quarter dish of their favorite sushi and eat it.
At the end of the day, you take your empty quarter plate up, and are charged appropriately.
The quarter plates are actually color coded.
For example, a yellow rimmed quarter plate always contains shrimp sushi and krab sushi (not crab sushi).
A blue rimmed quarter plate might hold a more expensive eel sushi.
Green rimmed might be an expensive tuna…
The point is, when you were finished eating, you took you empty plates up to the cashier who counted out the different color plates, knowing that each plate has a certain ¥-value.
Yellows are ¥100 yen; Green ¥240; Blue ¥175… just as an example.
Which is why placing these sushi baggage wraps atop an airport luggage container is an amusing proposition.
PS: The egg sushi, seen second from the lower right, is my favorite. That and eel.