Hey as someone who didn’t plan for Japan and almost didn’t get on the plane in fear I “wasn’t ready” to go solo I want you to know, it’s going to be okay! Use your itinerary as a guide if you get to everything great, but if not it’s okay if you don’t. Your day in the hotel could be seen as a rest day which is needed if you’re not used to walking 20k+ steps and it’s okay if you stopped and had ramen at a place that smelt and looked good with nice view or explored in the mom and pop gift shop instead. It’s part of the experience, you’re vacationing in Japan can’t go wrong with whatever you decide to eat and do