Or you get a squatter toilette. Also you need to bring your own paper for a lot of public toilettes. Though it has been almost 20 years since I last visited. At the time I wondered why they handed out so many advertising Kleenex travel size packs. It was for the train station bathroom.
"In Japan, these high-tech toilets are everywhere: hotels, restaurants, bus stations, rest stops and around 80% of homes."
https://www.npr.org/sections/money/2020/02/25/808791622/why-...
The quote is somewhat exaggerated but mostly true. I've even found the public toilets to be incredibly clean. While it is possible to occasionally find older porcelain squat toilets they are becoming very rare.
https://www.bing.com/images/search?q=public+toilets+in+japan