Transportation after long flight

hello.
is it right , after long long flight, to take jr train to hiroshima from kanasai airport?
or it`s better to stay in osaka for a night (and if so, where) and morning after to take jr train to hiroshima?

Depends on how long the flight, how late you get into Osaka, how well you sleep on the flight, wher ein Hiroshima is your hotel and the ages of your travel group.

Last trip to Japan, I went from Narita Airport to Osaka by train right after arriving. I have a long flight (14.5 hours direct) For me, it was tiring, but I could manage. It was much harder for my child and she ended up in tears because by the time we got to our hotel it was 22:00.

For us, my kid is always up super early in the mornings for our first week due to jetlag. It's one reason I like starting in Kansai. I think it has better pre 8:00 am activities than Tokyo. But again this really depends on your travel group/style.

Our next trip we are probably going to do Narita to Kyoto. However, this time we won't have a rail pass and will be paying out of pocket for our train. That will shave quite a bit of time off our travel and will reduce waiting for a 2x an hour Hikari. It sounds weird but being able to take a more frequent train that is also faster I expect will happily alter things.

Good luck!

To me, a long ride on a Shinkansen is very different, and much more tolerable, than a long ride on a plane. On Shinkansen, you can walk around freely to stretch as needed and the leg room is longer thus more comfortable. If your arrival time is not too late and you have no business between KIX and Hiroshima, I would consider going to Hiroshima on the day of arrival.

Also consider that you wont be allowed to your hotel room in Osaka until 15:00 (unless maybe you find a very special place that allow early checkin). So if you are arriving realatively early in the day and think of relaxing in your hotel room for the rest of the day, that wont work, so better to continue on to Hiroshima directly.

Enjoy your trip to Japan!

No problem really. Shinkansen ride is a treat after long hours in plane.
I actually have used airport shower after arrival, think it was in Kansai. And don't forget to crab ekibento and coffee to train.