Hiya,
Sea shipment is 計體積晤計重量的, but there's still limitation for each carton coz of the safety regulation.
I see quite a lot of Taiwanese student use http://www.sevenseasworldwide.com/ to move back home.
I used http://www.nipponexpress.com/moving/index.html when I moved to London from Tokyo.
You can read through their sites to have some idea about the procedure and information. I would suggest you to get some quotes from different companies for reference first.
Cheers,
ALL ANIMALS ARE EQUAL, BUT SOME ANIMALS ARE MORE EQUAL THAN OTHERS.