Sending and Storing Luggage in Narita Airport

I have been living in Hokkaido for a few months and will soon return home. However, I am hoping to do some travelling in Honshu before I return home. I have two suitcases, one large, one small, both heavy, that I would prefer not to have to carry around with me during that time. I'm hoping to send my luggage from either the New Chitose Aiport or the Kansai airport to Narita airport and store it there til I leave. Alternatively, store it at New Chitose or Kansai airports and then send it to Narita for the day I leave. While I can find information for sending and can find information for storing, I'm having troubles finding information for both. Yamato will only store the bag for a week and I need it to be stored for nine days. Does anyone have any information or other ideas? Please let me know! It would be a huge help!!!

I have heard some people say that Yamato agreed to keep their luggage for more than a week, may be worth a try. Otherwise, if you can afford it I would just send it first to some hotel where you plan to stay during your trip, and then from there to Narita.