As someone who has historically tipped 15-20% (for decent service) out of regard for our custom here in the US...
and as someone who recently discovered (yes, I realize I should have already known) that my home state of California is one of many where wait staff are required to be paid at least minimum wage...
and as someone who realizes that the whole custom for tipping wait staff is based on the fact that they DON'T make minimum wage so the tips are designed to get them to at least that level...
and as someone who knows that the wannabe actor who's taking my order will give me the stink eye if I don't tip him 20% so he can make much more than anyone actually thinks he's making...
...I can't wait to go to Japan.