Save yourself the trouble of hating life. Bring your Luggage to the convenience stores(I used Lawsons), you can have your luggage delivered as early as the next morning. You can choose at what time you want it to be delivered, to make sure that you will be there. It is quite nifty. Prices can range from 500yen to 1500yen, depending on the size of your luggage. Weight is not an issue.
If you have appliances that you don't have boxes for, contact companies like "kuroneko"(translated: Black Cat). They will provide boxes and deliver it. Price of this service varies. The amount of money you save by self delivering(train cost included) is not worth your time and mental health.
If you are lucky and have a Japanese friend with a drivers license renting a van is a possibility.
I lived in Japan for 15 months. And after my initial settling, I moved twice. I must say that moving has been one of my worst experiences in Japan, and one of the most taxing ordeal I've endured. You are not just physically tired, your mentally beaten down into mush. By the time your done, you feel like a shell of a human being. I never appreciated living in the states more.
The U.S. is a lovely country in which everyone drives a car, and nice fit lifting capable friends are not hard to reach.
When it come to moving by yourself as Gaijin, it straight sucks in Japan. Oh...and by the way...no matter how small you are..or how big your luggage is...NOBODY WILL HELP YOU! This is no joke, when you see someone struggling up the stairs with large luggage, normal instinct is to help. Not in Japan though, the luggage can be 1 to 1 ratio in weight and mass to the person carrying it, and no one will even bother to help. They just walk past you...watching your sweat pour into your eyes. (by the way: elevators are not as well placed as you may hope. And they only exit in the larger stations)