[jinto36]

Yeah, there really isn't a good reason to drive unless you really want to go somewhere that doesn't have a train station. There are not all too many such places.

I'd also add a suggestion of renting a bike and riding the shimanamikaido from Hiroshima to get to Shikoku. You can also take a ferry and then bike back one-way from Shikoku to Hiroshima if you want. When I did it (2010) they only had "real" road bikes available from the Shikoku side for some reason, so when I showed up on the Honshu side I settled for a hybrid-ish mama-chari. I happened to have good weather (some time in July), made short stops at random shops on the islands along the way, and stayed a business hotel in Imabari for a couple of days, then rode back. https://www.japan-guide.com/e/e3478.html

That trip started with attempting to walk to Nagoya to Osaka, but I only made it 50 miles before giving up and taking the train the rest of the way, because I tried to save some money and bought junk shoes that wrecked my feet. This was of course when the exchange rate was 78 yen per dollar, rather than 150 ;) That was really frustrating since it was only a few months after I ran the Tokyo Marathon, and I figured I could handle any kind of foot pain by then. Nope, don't compromise on shoes when you're thinking about trying to walk 30 miles a day.