Hokkaido 3rd week of June

Hokkaido in late June is a great choice, as the rest of Japan will become hot and humid. Hokkaido is famous for onsens (soaking hot springs) , excellent seafood, and natural scenery. Since there are the three of you, you can opt for renting a car when you are not staying in major cities (Sapporo and Hakodate). There are some sleeping volcanoes by lakesides, where nice resort hotels are located. Have you checked out https://www.japan-guide.com/ and https://www.visit-hokkaido.jp/en/ ?

Love Japan, love Honshu except in the hot muggy summer, love Hokkaido.

You have a tough one here. For a first trip to Japan, yes, it makes sense to hit the major sites in Honshu: Tokyo and lots more. But man, it's gonna be hot and humid, and after 2 weeks there, you're gonna be happy to head north (actually, you'll be wishing you could head north after a few days...). In June, Hokkaido is blissful. There's too much to see and do in just one week - there's the rub. I'd consider flipping your script: knock out Tokyo and one or two more brief stops in your first week, then head north to Hokkaido for two weeks. I know, I know - there's so much to see and do.

We went around much of Hokkaido and loved every bit of it: way up in the northwest, Rebun Island is lovely, the north coast is also cool. In the east, Shiretoko National park is spectacular. We also loved the mountains and onsen towns around Daisetsuzan National Park. The flower fields, gardens and rice paddies in the west-center, around Biei and Furano are beautiful - check out the lavender fields, too. Otaru is a cool old town with canals and a rich history.

We caught a baseball game in Sapporo, and got to see Shohei Ohtani before he came to America to play (his team was the Sapporo Ham Fighters - Fight That Ham!!). Japanese baseball is quite a hoot, try and catch a game if you can.

We drove all the way - Hokkaido makes for a great, classic road trip. Easy driving (once you get your brain and muscle memory to switch sides...). Be extra careful for the first 30 minutes of driving (and watch out every time you come to a stop and turn left or right onto another street).

I want to add that renting a car in Japan is very civilized and stress-free. The agents won't rip you off for "damages" that you never make. Drivers there are polite and sane.

As mentioned, it does take a while to get used to driving on the opposite side of the street and reading speed signs in metric.