I'm American, so from a tipping country, and can say that I don't miss tips in Japan. I have been here for 5 years now, and it never really crosses my mind.
Service in Japan is very "by the book". It's manual service. So the service is good, but you get the same service from every employee.
There are also more rules to social etiquette in Japan than there are in the states, I my humble opinion. If tipping were introduced in Japan, I bet it wouldn't be long until everyone always gave the "recommended" tipping amount no matter what the level of service. Be it 12%, 15%, whatever, they would abide by it to the yen. After time, it would just be added onto the bill anyway.
If you go to fancy bars in Japan, occasionally people will tell the bar tender to "keep the change". This could be considered tipping. It never happens from what I have seen, at restaraunts though.
Likely the waitress would come chasing you down the street telling you that you forgot your change!
すみません！お客さん！おつり忘れてるよ！！！
BTW, what other countries tip other than the US?