Does that mean any offer of a favor has to be repeated four times, or else is insincere?

I've not been to Japan, but heard what seems to be an exception to this rule from a colleague.

When out having drinks, it is considered (1) rude to let your friend's drink go empty, and (2) rude to refuse your friends offer for a drink.

Is this accurate? If so... one can imagine how this can get pretty messy!

I wouldn't know, I've never gone drinking with Japanese people, just been friends with Japanese Americans as a kid. It's a thing.

I don't know if Japanese Americans truly represent their country of origin. If it's like Italian Americans and Greek Americans they tend to have customs that in their country of origin are outdated.

There are at least some Japanese Americans that do this, who then informed me that it's a thing

Rude seems like a too strong a word for it but it's normal culture to fill someone's cup if it's empty and it's rude to poor for yourself without first filling your friend's cup, and ideally they'll ask for the bottle to fill yours once you've finished filling their's but it's common to just fill your own after filling theirs.

As for (2) I don't know any culture where if a friend asks you to meet up with them that there isn't some expectation you'll accept the offer and if you can't you'll at least try to make the friend feel you'd really like to but for whatever reason you can't right now. If you just responded "no, I don't want meet" I'd except after a few such responses you'd no longer be friends in any culture.

(2) is perhaps poorly and ambiguously worded on my part. What I meant to convey was: "It's rude/impolite to refuse your friend's offer to top your drink up" (context being: you're already out drinking).

Take the drink, and let it sit there full to indicate you don't want more.

In Iran when you ask a store owner the price of something, the answer is "It's free." Then you have to refuse a few times if it's free and then you can get the price. (Not my personal experience. But I heard the same thing from a few people.)

This is called Taarof and can be at times quite extreme: https://en.wikipedia.org/wiki/Taarof.

I have a good friend whose parents are from Persia/Iran. He told me about this culture after we knew each other for quite some time. Even though he has never lived there, he often still has a hard time not to do this, which has resulted in some funny (at least for his friends) or uncomfortable situations over time. Knowing this, many things I ascribed to his character alone suddenly made a bit more sense.

That sounds like my worst nightmare, haha. I don't run into too many folks from that culture, but this is really good to know about should I find myself talking to someone who follows a similar custom. Thanks for the link!

Thanks. I didn't know that it was a general thing and had a name. Fascinating.

Same in Arabic culture.