Also, if you travel during the school year, you may run into herds of children and teens being taken on class trips.

This is a particular hazard in Kyoto and Nara.

I once arrived in Nara in May only to find that it had been taken over by 13-year-olds in various school uniforms.

They were harmless and even charming at times, but there were so many that they literally blocked some of the narrower streets as they sauntered along window shopping, stopping for snacks at vending machines, and talking, either in person or on their cell phones.