Sure, when they are closer to 10 instead of being closer to 5 years old. My children were 5 and 6. They need to be 7 to take the train alone.

And yeah, I lived in Shinjuku 5 minutes walking from the largest subway in the world in terms of people going through and it and physical size. It was a busy area.

This is the apartment I lived in - https://tokyoapartmentinc.com/room/17207/

http://www.rental-apartment-tokyo.com/?post_type=fudo&p=2036...