I wrote a guide about playing in Tokyo (https://pokemongohub.net/user-guides/tourists-guide-pokemon-go-tokyo/) but I also played a bit in Kyoto; I’ll recap my experience for you.
Kyoto is another large city in Japan, so similarly to Tokyo, you’ll find a lot of people playing there. Pokemon Go is still one of the top games in Japan. You should have no problem walking up to a raid and finding people there. Something to keep in mind is that people do not often talk during the raids; they kinda just stand to the side of the sidewalk and look at their phones (at least in my experience in August 2017; maybe it’s different now)
As Kyoto is a large city with many people, you probably won’t have trouble with finding people to raid with. However, in Hikone and Himeji, it might be a little harder (but who knows for sure; a lot of people play this game + you could find tourists playing there too).
Theoretically, people will come and go to raids. You just need to look out for people.
If you want to ask someone if they are playing Pokemon Go in Japanese, you can say this (I’ll write it how its pronounced): Sue-e-ma-se-n, Poh-keh-mo-nn Gooh wo yat-teh-i-ma-su-ka? (Excuse me, are you doing Pokemon Go?) Worse comes to worse, just show them your phone screen. I’m sure many people will recognize it.
Hope this helps!