3 Week Itinerary Help (June)

Hi!!

My siblings and I are planning a trip to Japan for 3 weeks in June! All three of us have differing interests in what specifically we would like to see, but we would all like to travel together. The following is our very rough itinerary (we're intentionally keeping the day-to-day activities unplanned for now, as we know that overextending in that regard can be a common Japan travel pitfall). No matter what, we are all looking to have a good balance between scenic nature & city life. It's our first time going to Japan, so we're looking to hit up the places you can't miss.

Feedback that I'm looking for:
1) Is this amount of travel between cities unfeasible for 4 college-age adults?
2) Are we spending too much/too little time in any locations
3) Are there any glaring omissions (places close to Tokyo/Kyoto/Osaka or on Tokaido/Hokuriku shinkansen lines)

Day 1
Land in Tokyo

Days 2-4
Tokyo! (w/ one day allocated to day trip to Nikko)

Day 5
Train to Kanazawa

Day 6
Kanazawa

Day 7
Train to Kyoto

Days 8-11
Kyoto (w/ one day allocated to Nara)

Day 12
Train to Osaka

Days 13-14
Osaka

Day 15
Train to Hiroshima

Day 16
Train to Nagoya

Day 17
Ghibli park day in Nagoya
Train to Kamakura

Day 18
Kamakura

Day 19
Train to Tokyo

Days 20-21
Tokyo

Day 22
Fly back home

by Enough_Resolution701