10 days itinerary advice (2nd visit)

Hi everyone,

We're going to Japan again from the 25h August to the 2nd September, it will be our second visit.

We spent 20 days there in 2016: roughly a week in Tokyo, a week in Kyoto and the rest of the days around Kanazawa and Takayama. We're a couple in our early 30s, last time we went with our toddler, this time we're going on our own, so we'd like to focus a bit more on nature.

We arrive in Tokyo early on the 25th and leave from Nagoya in the evening of the 2nd. We'd like to go to Nikko, more for the National Park than the Toshogu Shrine. Then we'd do Kamikochi in the Chubu Sangaku National Park. Then we'd like to head towards Okayama prefecture, to see Koraku-en and also the city of Kurashiki. If possible we'd like to spend a night in Mt Koya.

We have an idea of itinerary but since we want to see national parks we find more difficult to plan ahead than cities, we're not sure about how much time staying there. Also since we won't be in major hubs we're not sure if we will spend too much time traveling, so maybe it's too crazy and we'd like some feedback! We tried to put some city stops in the middle to make it more feasible:

25 - Arrive 7am, travel to Nikko from airport, spend day and night there
26 - Spend some of the next day in Nikko, head to Kamikochi via Tokyo (I understand we have to go via Tokyo then Matsumoto?)
27 - Kamikochi
28 - Leave for Okayama, see Koraku-en
29 - More Okayama, day trip to Kurashiki
30 - Leave for Osaka (maybe stop by Himeji Castle in the way?), spend day and night there
31 - Leave for Mt Koya in afternoon, spend night there
01 - Leave for Kyoto in the morning, spend day and night there
02 - Leave for Nagoya late afternoon just to take the flight (departure 9:20pm)

Many thanks for you time and advice!
Sam

I would recommend the following itinerary, since some of your trip is very long (Nikko to Kamikochi).

Use Japan Rail Pass 7 days from 25.

25 - Arrive 7am, travel to Nikko from airport, spend day and night there
26 - Stay Nikko, or Matsumoto (Nikko to Kamikochi is too long and note that Kamikochi closes very early --17:00 i think).
27 - Kamikochi
28 - Kamikochi
29 - Kyoto
30 - Leave for Okayama, see Koraku-en. Stay in Okayama (Kurashiki)
31 - Leave for Mt Koya, spend night there. End of JR pass.
01 -Leave for Osaka (Namba, which is convenient for both Koyasan and Nagoya, spend day and night there.
02 - Leave for Nagoya late afternoon just to take the flight (departure 9:20pm). Use Kintetsu Limited express which take more 50 min but cheaper by 2500 yen than taking Shinkansen.

You might better switch Koyasan and Osaka (Namba) to increase time in Okayama.