[jasonbvr]

There is the delivery service Kuro Nekko (Black Cat) which will ship your stuff for a decent price. I've taken my snowboard gear, and will again, on the shinkansen. I just leave it in the area where you board the train then sit near the door. But yeah, there is barely room to stuff a book bag above your seat on the shinkansen. However, there are different models of trains so I have no idea what runs between Tokyo and Osaka. If you are really concerned about luggage and really wanted to do the budget trip, take the night buses.