Japan 21 days itinerary

Hi Folks.
I've read a bunch of different variations on the 21 days in Japan itinerary but here's my plan. We would like to get a feel for big cities and small towns so I've tried for a mix of things, never spending less than two nights in any one place.

October 11.
Fly into Tokyo Haneda
Stay in Tokyo for 7 nights
- day trip to Nikko on October for Toshogu Shrine Festival
- possible day trip to Hakone?

October 18
Travel to Takayama
Stay for 2 nights
- day trip to Shirakawa-go?

October 20
Travel to Kanazawa
Stay for 2 nights

October 22
Travel to Osaka
Stay for 2 nights

October 24
Travel to Hiroshima
Stay for 2 nights
- day trip to Miyajima

October 26
Travel to Kurokawa via Kumamoto
Stay for 2 nights
- pick up rental car in Kumamoto and drive to Kurokawa to avoid buses and to use for possible day trip out of Kurokawa

October 28
Travel to Kyoto via Kumamoto
Stay for 4 nights
- day trip to Nara

November 1
Travel to Tokyo Haneda Airport to depart in evening.

Having looked at this suggested itinerary, I don't think we are trying to pack way too much in.

My questions are:
- Is the day trip to Hakone a must-do given the rest of our plans? We will hopefully see Fuji from the train when we are travelling past that area multiple times. Also, we will do onsen in Kurokawa so no need to double up on that.
- Is my plan to hire a car in Kumamoto instead of taking the buses crazy? I'm not worried about driving on the left hand side of the road, and with GPS I figure navigation will be fine too.

Thanks for any and all feedback provided. This board has already been a gold mine of advice trolling through other peoples questions :)

Sounds like a great plan. It will be a lot of repacking when only staying 2 nights in each city as you travel south, but I have done it before with no problems. This itinerary is very do-able.

A full day in Miyajima would be great. Make sure you get there in time to see both low and high tide. There are some nice hour to two hour long hiking trials to the top of Mt Misen (depends how fast you hike and if you stop to take pictures). I did this between High and low tide last time I was there and it was great!
Hakone is not a big city and it is a miss if it is raining. With everything else you will be seeing (unless you are going to Hakone for a day at the hot springs) it is a miss.
Kanazawa - I would make sure to see Ninjadera and the gold museum.

It is not crazy to drive instead of taking the bus; with GPS and if you are comfortable driving on the left side, then there should be no problem.

Hope this helps.

Thanks for the feedback. We plan to travel light for the periods of time between the big cities.
Since learning about the takyubin service we are planning to ship our bigger suitcases via that :)
We are doing 2 nights in kurokawa specifically for the Ibsen I feel much better about skipping Hakone now.

General consensus or at least what I feel is, a night at Hakone will make the trip more worthwhile due to the size and amount of attractions available in that area.

Renting car is always a good option especially to reach places with less than convenient public transport, as long you are convenient with driving in Japan..

Shirakawa-go, would be best if you could just stay for a night there, and you could take the bus to Kanazawa from Shirakawa-go. That's one way to do Takayama- Kanazawa trip.

Rest looks ok, if it was me, I would split up the Tokyo days with some days allocated at the end of the itinerary.