The sink drain. Yep, the kitchen sink drain in Japan.
What I was used to in the US:
A.) a shallow basket to catch debris before filtering water into a narrow drain (old style), and
B.) same as A. with a garbage disposal and larger opening to the drain (garbage disposal style).
While still commonly found in older homes in the states, this type is slightly less convenient because we really have to throw away any stuff left on our dishes before washing them. It’s not a terribly different drain, just more likely to get clogged or stinky.
Garbage disposal style
Some people peel potatoes and run the peels down the garbage disposal. They are chopped into little bits and mixed with the water supply. Some people mostly filter out any big bits of food the way they would with an old style sink drain. Either way, there is bound to be some gunk and leftovers that end up getting through the little filter basket. By running the garbage disposal, these are somehow magically whisked away.
(Not that either of these is better or really makes more sense than the Japanese design.)
Japanese sink drains
As you have seen on Mario, all pipes in Japan lead to Koopa.
In Japan we have a large (14cm) drain opening for most sinks, although there is a smaller size for mini-kitchens with itty-bitty sinks. Under a flappy cover/filter, we have a deep basket (or strainer) with tiny holes.
What I thought was the reason for the Japanese design:
When I first moved to Japan, I was laughed at by a coworker when I asked if this strange sink basket was designed to keep cockroaches from climbing up through the pipes. That was really my only idea as to why sink drains would have a weird basket like that.
The real reason for the Japanese design:
The obvious reason is to catch food debris (and random things that slip through the flappy cover/filter). I could have lost a potato and probably some chopsticks just in the last few months, down the drain, if it weren’t for the basket. There are always small bits of food that find their way into the (sometimes huge) sink, then into this basket. We then have to empty the basket’s contents into the trash. (I don’t think the depth of the basket indicates how full it should become before emptying.)
After living in Japan for a little while, I realized that the reason for filtering out even little bits of food is related to Japanese culture. If you’ve ever seen Miyazaki’s “Spirited Away,” you might understand that Japanese culture respects nature and water very much. To pollute the water with all these little bits of food is just not right.
Still, I wonder why the standard sink drain and basket is so wide and deep. In the 100 yen store, I saw some replacement baskets which are about half as deep. Usually Japanese design is so minimal and beautiful. Not so much here. We do have the option of a pink replacement floppy cover/filter.
I think regardless of how tiny the holes in the basket are, food gets stuck in them, and is sometimes there forever. It’s usually difficult to scoop out all of the gunk, and it’s always a disgusting chore.
Cleaning (or not)
There is a lovely slime that likes to form in the drain, on the basket, and all around it. There is usually a smell that comes with it. Slime is called numeri (ぬめり) in Japanese and you will see this word on products promising to remove the slime and smell from your sink.
There are chlorine tablets (aka "Slime removing agent for drains") that can be placed into the basket or even in a special not-flappy drain cover. Some are yuzu scented or repel bugs too. I don’t remember the results being fantastic.
One solution I used for a while is to buy thin mesh bags (normally used for the often triangle shaped kitchen waste baskets found in many sinks in Japan). These not only filtered out even more gunk, they also made it easier to remove the gunk and throw it away.
The logical solution would be to have a sponge or cloth reserved for cleaning the drain and scrub it on a regular basis. Preferably while wearing rubber gloves and using a friendly but abrasive cleaner like baking soda (重層). Maybe bleach? I prefer to mostly avoid thinking about (or smelling) the sink drain.
In conclusion, the topic of how to clean things in Japan could be a never ending story. Are sink drains different where you’re from? How do you clean yours & how often? Have you looked inside the drain near your bathtub yet!?