One thing I made a point of when first visiting with my son was that we weren’t going to just hit the tourist hotspots. 2 days in Tokyo to get grounded (and one day failing to climb Fuji because of bad weather) then we headed north - this was August, so Sendai, Ishinomaki and then Hakodate were welcome respites.
Second visit we managed to climb Fuji, then cycled the Shimanami Kaido. Subsequent solo trips I’ve come to love Nara & Osaka, got really lucky as the annual Shōsō-in exhibition was on in Nara - mindblowing.
Since then I’ve gotten really attached to Kyushu - Beppu, Aso, Kumamoto, Kagoshima and Fukuoka. So different from the UK, but somehow feels like home from home.