When we were in Japan my son walked to school when he was 6. Parts of the walk close to the school were supervised. It wasn't just allowed, it was expected.
If you have lots of luggage going to the airport, the "limousine bus" services (they are just coach buses) are a good option if you're near one of the pick-up locations.
Allowing two bags per person, it was cheaper for us and didn't need to send it two days in advance.
- if you're sending your luggage to the airport, check the deadline for sending, depending where you are sending from it could be 2-3 days before your flight
- hotels I paid at were cash only for this service (one of the few things I paid in cash, but likely depends on the hotel)
- some hotels did not take payments for sending, only supporting cash on delivery, so if you're sending to another hotel you should check if they will accept it
Sending from a convenience store is another option if those two last points are problems.
Another thing I thought of, the two times I needed it, the hotels sold cardboard boxes (a few hundred yen) and provided packing tape for free.
When we were in Japan my son walked to school when he was 6. Parts of the walk close to the school were supervised. It wasn't just allowed, it was expected.