I have one day with no plans (city where to go)

Hello, I'd appreciate your insights. I'm planning a 10 complete days first time trip to Japan, starting in Osaka and ending in Tokyo. My original plan was going from Kyoto to Kanazawa, then the next day from Kanazawa to Hakone, but I think the trips are too long to make it enjoyable.

This is what it looks so far for each day:

1. Osaka
2. Osaka
3. Osaka>Nara>Kyoto
4. Kyoto
5. Kyoto
6. No plans for this day, originally Kanazawa/Shirakawago
7. Kyoto>Hakone
8. Hakone>Tokyo (planning rest day in ryokan)
9. Tokyo
10. Tokyo

I'm open to any suggestions, so far I have these ideas in no particular order:

1. Adding an additional day to Tokyo
2. Shortening my trip by one day, delete day 6 and adding it to my next destination after Tokyo (Seoul).
3. Shortening my trip by one day, adding to previous destination (Taipei).