The Mount Misen summit path should be doable with plenty of effort and stamina.
My father-in-law (in his 70s) and I took LapChild up to the summit of Takao San.
Wouldn’t earnestly recommend it at that age but it was doable... just. Have included a picture for proof as I’m still patting myself on the back in congratulation. It was tough. Saying that, had MrLapLap been with us it would have been less of a challenge.

Since LapChild turned 4 mountain and gorge hiking became much, much easier. We go up Takao San every year and very rarely take the cable car.
Mt Misen on Itsukushima (Miyajima) has very developed main paths that are similar in scale and difficulty to those on Takao San, thus the comparison.