Public toilets in Japan are available almost anywhere: inside convenience stores (one on every corner), on train/subway platforms and in public parks. If you feel the need to go, you are rarely more than a couple of minutes away from a public toilet.
More importantly, unlike almost everywhere else in the world, these public facilities are impeccably clean. They are cleaned regularly and, crucially, customers generally do a good job in keeping them clean. (Incidentally, most of the cleaning staff are women, and they clean the toilets while you’re standing there doing your thing; a little unsettling for some foreign tourists).
Here’s an example. I was visiting Kanazawa last week, and entered a public toilet in a small park. This is what the toilet looked like. Note the cleanliness, the availability of toilet paper, the facilities for disabled people, the diaper changing area… And all of this in a touristy area, i.e. with lots of customers.
(This is a post in the series “Why Japan is the Closest Place to Paradise“)