oh, tip 4 perhaps most important

4. Book rooms with Japanese family on AirBnb rather than hotels (Tokyo/Kyoto may be exception). So many times I managed to experience real local habits by being taken out with the hosts on trips on weekends, having garden BBQ with them and the neighbors, go wild "tent sauna" in the forest with the hosts etc. If authenticity is important to you - this is perhaps most important tip.