Please help with Japan itinerary

Add at least one more night in Kanazawa. One night does not even give you a full day.

Kanazawa is a nice destination but a bit out of the way compared to the other cities on your list. I am planning to be there in October and allowing a bit more time as well - several days to visit the city and the Noto Peninsula. The Kenrokuen Garden is a wonderful attraction and so I am allowing time to visit it during the day and then a second trip in the evening to see the illuminations which take place on weekends only, late October and early November.

Osaka is a short trip from Kyoto and may be worth considering. Lots to do and see there.

My experience is fairly Kansai centric, but here are some thoughts.

It looks to me like you have a lot of time in Tokyo. I don't know the city well enough to know if you need that amount of time.
There is a small ancient city called Nikko. It is an easy day trip from Tokyo. We enjoyed it. Take a look, it might be interesting to you.

Agree that two nights in Kanazawa makes a lot of sense.

Kyoto is wonderful. It is a bustling city in between all the tourist sights. Take a look at the Philosopher's Path. From memory, it takes you to some very nice, out of the way sights. Two of our favorite day trips are easy from Kyoto.

Nara Park is in the city of Nara. I expect you can get a walking map online or at the train station. Walking the loop around the whole park will help you feel like you are in old Japan. Feed the deer!

Himeji. The Himeji Castle is stunning and much better than some of the others. In Himeji, there is also a very rustic temple on Showa Mountain. Parts of the Last Samurai were filmed there.

My wife LOVES pottery. If this is a strong interest for you, look up Japan's ancient pottery towns and see if any of them make sense.

You might want to take a flight to another part of Japan with your open days. Perhaps either Nagasaki or Sapporo.

This sounds like a great trip.

Enjoy

Our itinerary was Tokyo - Shirakawa go - Takayama - Kanazawa - Kyoto - Mt. Koya - Tokyo. All good, but highlights were Tokyo, Kanazawa, Kyoto and Mt. Koya. Highly recommend a temple stay and nighttime walk through Okunoin Cemetery in Mt. Koya. Amazing!!

I fully agree with adding more time to Kanazawa. Once you make all the effort to get there, you should spend more time enjoying it. If you add to Kanazawa and Kyoto, you don't really need another three night stay. But maybe consider Nagoya as a possible destination. Or, drop Kanazawa (although I do love it) and add something else on your route, like Nagoya.

Given that you are devoting 8 nights to Tokyo and only 4 to Kyoto, perhaps you are more interested in modern Japan. If that is true, consider adding time in Osaka. If that isn't true, take time from Tokyo and add it to Kyoto to allow for day trips to Nara and Uji (could be done as a single fast day trip, but you'll miss a lot in Nara that way).

With 8 nights in Tokyo, you have time for day trips. Hakone could be done as a long day trip. Other rich choices include Kamakura, Kawagoe, Yokohama, and Nikko.

Final thoughts?

Tokyo (5 nights)
Tokyo explorations (Asakusa, teamLab, denim, Shimokitazawa, etc).

Kanazawa (2 nights)
Kenrokuen, Samurai District, Geisha District.

Takayama (2 nights)
Shirakawa-go stopover + Takayama Old Town; optional Okuhida onsen/ropeway.

Kyoto (4 nights)
Central/North, Arashiyama, Ine no Funaya, Uji+Nara, Southern Kyoto.

Kinosaki (2 nights)
Travel Kyoto → Kinosaki (2.5h). Yukata stroll + onsen-hopping. Next day relax, explore town fully (maybe Amanohashidate side trip).

Tokyo (3 nights)
Kinosaki → Tokyo (≈5h). Evening in Tokyo.

• Tokyo- Fuji day trip (Kawaguchiko: Lake, Maple Corridor, Chureito).

• Tokyo- Kamakura + Enoshima (or Mt. Takao foliage if we want nature/fall foliage).

• Tokyo → Flight Departure day.

Consider a day trip from Tokyo to Nikko, north of the city, its amazing.
Osaka is worth a day.

Any recommendation on number of days spent?

More days in Kyoto?

Takayama was my favorite place in Japan. Enjoy it all!

I have not been to Kawaguchiko, but some say that it's not convenient and that the surrounding areas are not as scenic. If Mt Fuji hides behind the clouds, then it may not be worth the effort to get there.

I suggest Hakone (stay at an onsen ryokan with a good view) for one night and do the tram loop.

I second that Takayama is not to be missed. There is a smaller but far less touristy town called Hida, just to the north of Takayama. Their streets are so quaint -- they are lined with canals with koi fish. Also, between Takayama and Kanazawa is Shirakawago village. This is another not to be missed destination.

When are you going in Oct? It's the beginning of foliage season at higher altitudes, such as Takayama.

Not sure if you know this: moving luggage on crowded trains in Japan is a hassle, but this wonderful country offers affordable "takkyubin" (luggage delivery) service. Your hotel can help you with this. I wish we had this service in the US.

Sort of a tangent, the Kyoto Handcraft Center is a good place to buy authentic items as souvenirs or gifts.

https://www.kyotohandicraftcenter.com/?lang=en