My husband and I (in our 70s but active and reasonably fit) will be arriving in Tokyo on April 20.

April 20 - arrive Tokyo, stay 4 nights
April 24 - travel to Kyoto, stay 6 nights.

These first 10 nights we are traveling with my sister, and this itinerary is set. She is departing Japan on April 30, and we have 8 nights to spend before we go to Seoul, South Korea on May 8. I now realize we will be in Japan during Golden Week, but we'll just have to deal with that. I had considered Kanazawa/Takayama, but my husband really would like to see Hiroshima. I know it's possible to do that as a day trip from Kyoto, but that sounds hectic and rushed.

I am looking for input as to our itinerary for these 8 nights. I am thinking perhaps 3 nights in Hiroshima (is that too much?), then go to Kyushu. It does not have to be Kyushu--that just seems like it might be a good fit location-wise. I am very open to suggestions. If we do go to Kyushu, I would prefer not to rent a car, but it seems as if a car is the best way to see Kyushu. Would it be practical to hire a guide there for some of the days? It looks as if we could then fly to Seoul from Fukuoka on May 8.

Any thoughts or suggestions are most appreciated.

IME, a half day is sufficient for Hiroshima. As you note, you can visit it as a day trip from Kyoto, though it would make for a long day. OR go for just one or two nights. OR go on your way to or from Miyajima. With the ease of transportation and luggage forwarding in Japan, short stays are much more manageable, IMO, than in most other parts of the world.

IMO, the ideal visit to Kanazawa and Takayama takes 5 or 6 nights. That means that with 8 nights, you can easily visit all three destnations.

Enjoy!

Is Seoul your only stop in Korea? One suggestion is to go from Kyoto to Hiroshima / Miyajima for a couple of nights and from there to Fukuoka to Busan, which is worth a few days. From Busan, you can take a train directly to Seoul.

IDK how GW would affect plans beyond it being a heavy travel time. Would look into opening hours/days and lodging availability.

Three nights in Hiroshima is not too much. It is more than is necessary. You would have a full day for the city sights including the Peace Park & Museum. Another day to visit Miyajima and some time for other nearby places (thinking Tsuwano). Spending a night on Miyajima would be worthwhile.

I love Kyushu. You certainly can fly from Fukuoka to Korea and ferries are available. I would book FUK->SEL (for Seoul Gimpo or Inchon) soon.

Go to japan-guide.com and search for Hiroshima and for Kyushu.

Gotta go, will be back

I wrote "soon", but no rush. Besides Fukuoka there are nonstops to Seoul from other major cities in Kyushu. Nagasaki, Kumamoto, Oita, and Kagoshima.

There are many flights from Fukuoka. Here are search results from those other airports to Seoul:
Kagoshima and 4 more to Seoul | Google Flights

Here are the Fukuoka flights for your day, all going to Seoul ICN:
Fukuoka to Seoul | Google Flights

You can have a wonderful visit to Kyushu without a car, just by taking the trains including shinkansen. You can reach more by bus.

Here is an overview of Q-shoe:
Kyushu Travel Guide - What to do in Kyushu

On that map, the city names are hyperlinks. Click on Fukuoka, Nagasaki, and Kumamoto. Those are the first three Kyushu places that I can recommend.

By bus from Kumamoto, there is a side trip to a town that I loved: Kurokawa Onsen Travel Guide - What to do in Kurokawa Onsen
Getting from there to Kumamoto Airport (KMJ) by bus was easy enough. There is also a bus to Fukuoka Airport.

I was just looking for a description of how attitudes are different in Kyushu from most of Japan. I sense a difference, maybe a bit laid back. Polite, of course, but maybe more furenduri.
About Kyushu | Kyushu Tourism Organization | Visit Kyushu

Thank you so much for your very helpful replies. This is our first trip to Japan, and I'm torn between these itineraries:

1) Hiroshima / Miyajima for 2-3 nights, then Kyushu, flying out of Fukuoka;
2) Kanasawa / Takayama for 5-6 nights, then perhaps two nights in Osaka, flying out of Kansai Airport; or
3) Hiroshima / Miyajima for 2-3 nights, then the 4-hour train to Kanazawa, then Takayama, then back to Kansai Airport. This one doesn't appeal to me as much because of longer travel times.

1) ok, but there are other options to FUK. You need to spend some time finding a Kyushu itinerary
2) fly from Toyama to Seoul
3) I don't like the travel times, either, considering you will be so close to Kyushu, like 90 min to Fukuoka, You have probably got input about Kanasawa / Takayama as they are popular. That is a good reason to go to Kyushu - if you plan it out and take the time to find out what is there for you.

Toyama is your best bet for those last two itinerary options. I've flown both ways between there (TOY) and Seoul, Small airport cmpared to KIX. Easy bus ride from Toyama station.

Komatsu Airport is closer to Kanazawa than TOY but I think there are no flights to Seoul from there, but u could check if u want to go there. Kansai? No, even Tokyo might be better.

You haven't mentioned what interests you have in Japan.

>> You haven't mentioned what interests you have in Japan.

You have, so far, only mentioned place names. Why do you want to go to Kanazawa? I know why to go there, but do you? Same question for the other places. Hiroshima is pretty obvious given its place in world history.

Is this your first trip to Japan? I can tell that you have done some research, but I don't have a sense of your interests.

Yes, this is our first trip to Japan, so I am spending a lot of time browsing travel forums to get some ideas. I also have a Japan travel book. That's usually how I approach planning trips.

Let's see--what interests do I have in Japan? I love to be immersed in other cultures. My husband and I are very interested in history, art, good food, big cities that are rich with culture, and also smaller, quieter places. That all sounds very generic, I suppose. We are interested in seeing beautiful architecture, temples, and gardens. I am an artist, and I love museums, both art and history. I always have a calendar of Japanese art on my wall; I have a gorgeous book of a kimono exhibit--I am entranced by this stuff!

We enjoy walking, moderate hiking, finding charming restaurants. We will deal with crowds when we have to, but we will balance that by seeking respite in more out of the way places. We are somewhat laidback travelers--I have no need to check everything off a list. I'd rather see fewer things and enjoy them. We are not interested in nightclubs. We are not interested in taking endless selfies for our social media accounts.

I am pretty sure I am going with the Hiroshima/Miyajima (2 nights, possibly 3), then Kyushu (5 or 6 nights) itinerary. It will take me more research to develop an itinerary for Kyushu, but it looks like that might be my cup of tea. We will then fly out of Fukuoka.

I definitely appreciate all of your thoughts and suggestions.

Thanks. Yes, a bit generic. You mentioned gardens and I asked why Kanazawa, but you didn't mention Kenrokuen, the v famous garden in Kanazawa. I love kimono and once visited a shop in Kanazawa where I saw an artist hand painting kimono in a regional style/method called kaga yuzen (Kaga being the old time name of the region). That was a stop on a high-end tour and they really wanted to sell me a kimono, as gorgeous as it was pricey. I just started reading the book Kimono by Liz Dalby because I loved her book Geisha about her first-hand experience as a geisha (geiko) in Pontocho, Kyoto.

You can probably find kimono-related places in Kyoto and Tokyo. You can rent a kimono and wear it as you visit temples, shrines, etc. That is, you have an opportunity to participate in and honor a Japanese cultural tradition and art (and am almost certain that is how it would be viewed by Japanese).

You have heard of Kobe beef. Did you know about Hiroshima beef or oysters Or in Kyushu the Saga beef or Kumamoto beef. Every region/city has some food specialty or style.

Kyushu is wonderful if you like hot springs. There are many scenic train rides on the island. Nagasaki has a long history. Go see a Fukuoka Hawks game even if you are not a baseball fan.

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I have to admit that when I read your description of interests, I immediately thought that you would prioritize Kanazawa -- a center of Japanese art with (as mrwunrfl notes) one of Japan's most beautiful gardens and an urban area, along with some small and interesting traditional areas. I'm not saying Kyushu would be a bad choice -- just surprising in light of your interests.

And Takayama not only has some unique cultural elements, but is also known some of its foods. It would seem a nice companion to Kanazawa for someone with your interests.

But its your trip and I'm sure you'll have a wonderful time no matter what you choose.

BTW, japan-guide.com is, IMO, without equal as a resource for information about Japan.