Travelling with backpack to a ryokan

Hi!
I'm going to visit Japan in August and I'm just organizing my itinerary. I'm not very experienced in travaling outside Europe, so the planning (even triffles) gives me quite a headache. Here's an example:

There seems to be many places that are worth just about a one-night stay, prefferably in a ryokan. For example Hakone. From my perspective it would be often convenient to arrive in the evening, spend the night, then do all the tourist stuff in the following day, catch a train in the afternoon and continue the journey to some further location.

But most of the times I'm going to travel with a big backpack and I'm afraid it may be troublesome. Can I expect to be able to leave my luggage at a ryokan after the check out, so I could collect it on my way back? Or should I rather strive to arrive and check in in the morning?

It depends on the Ryokan you will stay but the most of them will keep your belongs before and after check in and out but you must ask first there.
Your belongs must be clean and tidy.

If you plan to stay in a "ryokan" of the traditional sort, be sure to arrive early for the dinner there (or eat elsewhere and arrive late). Also, as traveling in/around Hakone can involve many different modes of transport, be sure to select a ryokan in a location that is convenient to "return to" for luggage pick-up at the end of your sightseeing. Otherwise it might be easier to forward your luggage to your next destination by courier service (next-day delivery).