You should never tip in Japan, no matter what. Service is impeccable here, and servers will go out of their way to make sure you get the information or whatever it is you might need, but tips are never expected. That includes all services waiters, taxis, hair stylists, hotel maids, everyone. If you try to tip you will only cause confusion; someone will think you forgot your money and you will embarrass people.
In general, there isn’t a whole lot of tipping in Asia, though I think there are many more exceptions than in Japan (and probably Korea too). In India however, tipping is known as ‘baksheesh.’ It’s institutional in all walks of life and sometimes amounts to extortion! And it’s odd too, because while service is generally quite good throughout Asia, in Japan it is quite often impeccable. So if there is no tip, where does the motivation to provide good service come from And why is it that in the West, where service is sometimes poor, a tip is expected anyway
I don’t know the answer to that question but I can say that Japanese society is highly ritualized, even down to the art of ‘masking’ (I would not say ‘faking’ exactly) emotions. So if someone servicing you is smiling and genuinely looks kind it might be only that- looks. Which is not to say that the person is actually seething on the inside, it’s just that in Japanese culture, presenting a pleasant face and showing a polite demeanor is part of the job. Naturally, the waitress is a stranger, not matter how friendly she seems. Tipping in Japan, simply put, is alien to the culture and obviously always been.