[discoiskinky]

I dont know if this is a plausible option for you but to resolve the issue of not knowing where to lock up your lugguage if you fly into Osaka, go directly to the hotel you plan to be staying at from the 13th until 16th and get them to hold your suitcases until you check in on the 13th.

This way you will only need to bring a small bag with you for Hakata and when you get back to Osaka your bag will be waiting for you at your hotel.