Hi,

A couple of suggestions

Iwakuni ( short train and bus journey from Hiroshima) is very nice with a beautiful 5 arch wooden bridge ( kintaikyo) and various parks and a ropeway to the Iwakuni castle ( small but great views). It is on the local line from hiroshima a few stops beyond Miyajimaguchi ( JR ferry to miyajima island) so you could do both in a day ( but for a first time visitor both Miyajima and iwakuni deserve separate visits imo)
Iwakuni Travel Guide - What to do in Iwakuni

I would probably choose either Nara or Kobe for a day trip ( and not to do both on the same day). There is a lot to do in Nara ( temples and gardens as well as the deer in the park). I stayed there for 2 nights in May 2025 ( very wet for one day but enjoyed the museum)

Nara Travel Guide - What to do in Nara City


Onomichi is beautiful but with lots of steps and slopes to the temples. I was there in May but it was very hot amongst the temple path and gave up the temple walk and took the ropeway to the observation platform on Senkoji park with great views and a pleasant breeze which was a lot better ( I stopped at Fukuyama ( very nice castle 10mins from the station enroutre back to my hotel at okayama)

Regards

TBS