No tipping is the norm in Japan. Even at family Denny’s type restaurants. Yeah, the food is a bit more expensive (as is everything else), but calculated as a percentage of take-home pay or hours of labor, it is remarkably similar in price.
I worked at a country club for 10 years where no one left tips because a 15% gratuity was added to all bills. That 15% was split between all waiters/waitresses, bartenders, barbacks. etc. By the time they got done with it it was split between 20 people so we got crapola in tips added to our checks.
The only thing that kept me alive was banquets, lots and lots of banquets where I made excellent money in cash tips. If I couldn’t have worked them I would have quit.
This is true, and I would add that, particularly in the Kansai region (Osaka area), tipping is considered offensive, because it implies that the restauranteurs would not be providing good service otherwise. OTOH, restaurants there are generally more expensive than in the US, even with the recent dollar/yen reset, with the exception of the "family" restaurants like Denny's and Saizeri-ya, which cost about the same in Japan as in the US.