I did this trip with JY in April 2023 and you will find my review here https://forum.justyou.co.uk/Posts/t127749-Japan-revealed---8-April-departure 

There is always walking on these tours but with reasonable fitness you should be OK. Most walking was on the level with the occasional slight incline. As I said in the review "nothing too onerous".

As regards early starts then define early! Our earliest start was on the last day to get from Kobe to Osaka for the flight home. However JY are now using a different airline with later flighty time so provided these do not change that will not apply. Looking at my own diary notes then departures were generally around the 8.00am mark each day but cases may need to be brought down somewhat earlier on travel days.

Anything more specific then feel free to ask.

Ian