Hello Daniel thank you very much for your reply. I will consider your suggestion about Naoshima.
I calculate all the train fees, if you have time, please tell me if I did some mistakes
Day 1 : Hiroshima ( arriving from Paris to Hiroshima)
Day 2 : Hiroshima
Day 3 : Hiroshima-Miyajima-Hiroshima 410 X 2 + 180 X 2 = 1180
Day 4 : Hiroshima-Iwakuni-Hiroshima 760 X 2 = 1520
Day 5 : Hiroshima-Okayama = 6020
Day 6 : Okayama-Naoshima-Okayama = 580 X 2 + 290 X 2 = 1740
Day 7 : Okayama-Osaka = 6020
Day 8 : Osaka-Kobe-Osaka = 410 X 2 = 820
Day 9 : Osaka-Koyasan-Osaka ( not covered by Jr Pass )
Day 10 : Osaka-Kyoto = 560
Day 11 to 14 : Kyoto
I will add 1000 jpy per day for train/subway/bus
So I have a total for the first two weeks of 31860 JPY and the JRPass for 2 weeks is at 46390 JPY. That is why I thought that the JRPass was not interesting for my two first weeks, but …..
Day 15 : Kyoto-Nara-Kyoto 760 X 2 = 1520
Day 16: Kyoto-Ise : 8030 using JR network only
Day 17 : Ise-Tokyo 12990
Day 18 : Tokyo
Day 19 : Tokyo-Nikko-Tokyo 5580 X 2 = 11160
Day 20 : Tokyo-Kamakura-Tokyo 920 X 2 = 1840
Day 21 : Tokyo-Kawaguchiko-Tokyo 3150 X 2 = 6300
For the third week we have a total of 41840 JPY. Which means that for the entire trip, it will cost us 73700 JPY per person if we choose to buy ticket by ticket. The 3 weeks Jrpass is more interesting because it will cost us 59350 JPY
Maybe it will be cheaper for us to arrive directly to Osaka, to use a Kintetsu pass for 5 days in the Osaka/Kyoto region, and then to take a 2 weeks Japan raill pass for Hiroshima/Okayama area for the first week and Tokyo area for the second week
What do you think of that ?
Thank you very much for your kindness
Best regards
Christophe