I had something similar, but it was near a school. I was looking for my Airbnb the first time visiting Japan. It was on a smaller street with very few people. I was standing behind a line that was at a school. The volunteers came over and told me I can't stand behind the line since that is the school. Moving 3 inches made it automatically ok.
The volunteers was very nice and didn't tell me whatever society bullshit. Just that I can't be near the school unless I'm picking up my kid