Sorry, to clarify.

I plan on taking the Shinkansen down into Kyoto on Saturday afternoon. After I arrive I'll need something to do with my bag, as I'm going to a concert during the evening.

I'm then planning on heading to Osaka to spend the night (because money is an object for me, I'm a University student and the only hotels in Kyoto and Kobe with rooms available that weekend are quiet expensive) -- The crown plaza actually has no rooms available for the 5th..

I'll leave Sunday after heading to check out for Kobe, and attend another concert there. Hence the need for to do something with the bag. After that I'll take the Shinkansen back up to Tokyo (the last one of the night) to get home by Sunday night.