This Takkyubin service is great. I stayed at the Keio Plaza hotel in Sapporo. They had a Takkyubin desk in the lobby. I used it to send my larger bag to my hotel in Tokyo. Cost was 1730 yen. Note: they weren't offering next day service, it was two day service for bags dropped off before 630 pm.

I stayed at the Park Hyatt Tokyo.I just called the bell desk before I check out and told them I wanted my bag sent to the Hilton Osaka. They filled out the forms and gave me the receipt and sent the bag to Osaka the next day. Cost was 1400 yen, Park Hyatt just billed it to my room. Bag was waiting when I arrived at Hilton Osaka next afternoon.

I don't know the costs/feasibility of sending bag back to USA. The lady at the desk at my Sapporo hotel said the service was for Japan only. I think you could always have your bag shipped to your departing international airport though and then collect it and check it for your overseas flight.