12-day Japan itinerary advice

Hello,
My wife and I will be flying into Japan from Hong Kong for a 12-day visit in mid-August. We arrive in Osaka and plan on making Kyoto our home base for the first half of the trip, and Tokyo the second half of the trip (flying out of Tokyo). There are so many wonderful options for day trips from both Kyoto and Tokyo, but I want to ensure that we get at least 3 full days/nights in each of these cities to get the full experience. We are both in our early 30s, and are interested in a well-rounded experience (traditional + modern). We will likely buy the JR pass. Our preliminary itinerary is below, and any suggestions/advice will be greatly appreciated.

Day 1 - arrive Osaka in evening, train to Kyoto
Day 2 - Kyoto
Day 3 - Kyoto
Day 4 - Nara (day-trip)
Day 5 - Kyoto (or Osaka day-trip)
Day 6 - Hiroshima/Miyajima Island (stay overnight, ?ryokan)
Day 7 - Travel to Tokyo +/- spend night in Hakone (?ryokan)
-?stop in Himeji
Day 8 - (Hakone/)Tokyo
Day 9 - Tokyo
Day 10 - Tokyo
Day 11 - Kamakura (day-trip)
Day 12 - Nikko (day-trip) vs Tokyo
Day 13 - Tokyo/fly out

Main questions are: 1) is it worth doing a day trip to Osaka instead of spending a third day in Kyoto? 2) Are ryokans in Miyajima Island the same quality as in Hakone? 3) Will it be difficult to travel from Miyajima to Hakone and/or Tokyo in one day? 4) Is it worth going to Hakone? I've read the views of Mt. Fuji are hit or miss from there, but are there other locations to get a good view? 5) Kamakura vs. Nikko, in case we decide to cut one out in favor of another day in Tokyo?

Thanks again!

Day 6 and 7 are very rushed. Kyoto to Hiroshima is about 2 hours. Hiroshima to Odawara is about 6 hours (+60 mins from Miyajima). You have day 8 to do Hakone as Tokyo is only 40-90 minutes depending on train used.

You really only have time for Miyajima or Hiroshima. If you wanna see both, I'd add a night.

1. You don't need to decide on that now since you won't be changing accommodation. You can decide after 2 days in Kyoto whether there are more to see, or explore Osaka. Personally, I would continue in Kyoto.

2. There are all kinds of ryokans in both Miyajima and Hakone (very expensive to moderate). Hakone being bigger offers more options.

3. No.

4. Hakone is very popular, because (a) it is close to Tokyo, (b) it has good Onsen, (c) there are lots of other things to see and do besides Onsen. If your main purpose is to see Mt Fuji, there are better places (e.g., Kawaguchiko). But even in Kawaguchiko, the weather may prevent good viewing of Fuji.

5. Kamakura or Nikko? I personally like strolling in Kamakura, but for the first timers I would recommend Nikko. Both places has lots of temples and shrines, but Nikko's Toshogu is quite different from most other shrines and its gate was recently restored (and it is spectacular!). Nikko also has the waterfall (Kegon Falls).

Ok thanks to both, great advice. Do you think a trip to Hiroshima/Miyajima is recommended in this itinerary or should I add that day to an extra night in Hakone? Also, is it easy to transfer luggage between hotels in different cities; for example, transferring luggage from Kyoto to Miyajima if we don't want to store while exploring Hiroshima?

Up to you whether you drop it or not. Depends on you interests. Many of you destinations are quite different offerings. So depend on what ''you'' really like. Nikko vs Hiroshima? Mountain scenic vs Coastal scenic? You are already doing mountain scenic with Hakone.

Whether going to Hiroshima/Miyajima is worth it or not ultimately is up to you. 1 day may or may not be enough depending on what you're trying to accomplish. If you're just trying to hit the main tourist sights (Itsukushima Shrine, Hiroshima Peace Memorial Park), then a day-trip is possible. For example, you can start off early in the morning and do Miyajima in the morning/noon, then go to Hiroshima in the afternoon/night. Again, only you can decide whether it is worth it.

I have travelled to most of the locations you mentioned in about 18 days. First and foremost I would like to agree that you need at least 3 days but preferably 4 or 5 to see all the highlights in Tokyo and Kyoto.

Looking at the schedule I would do the following changes:
- stay in Osaka for 2 nights upon arrival. Dotonbori is a lot of fun in the evening and great food all around. Next day do Nara from there.
- doing Hiroshima and Miyajima in one full day is possible. Just don't expect to go up the cable car on that same day. I would travel there from Osaka first so you can visit Kyoto after. That way you can avoid having to travel a full day when going back to Tokyo. If you would do this visit from Kyoto you first have to travel back to Osaka again.
- consider a stopover at Himeji castle on your way to or back from Hiroshima.