[staunch]

Have you ever actually experienced this or are you repeating the same myth? No one will be offended unless you're some kind of jerk about it.

"Do as the Romans do" is always the correct behavior, but in this case the potential for offense is entirely overblown.

[6t6t6]

I live in Japan and my wife is Japanese. Also, I had this conversation with several Japanese people.

I can tell you that most Japanese I know hate the concept of tipping and it makes them uncomfortable. They also hate giving tips. Not because of the money, but because they think that tipping is a way of looking down the other person.

Of course, when I say offensive I don't mean that they will curse and hate you forever. But probably some will think: "I already have a salary, I don't need you give me your coins".

If there's an scale of socially awkward situations, I guess tipping would be slightly under asking ketchup for your sashimi. But definitely not as bad as going into someone's house with your shoes on.