So here's what I found after two full restless days of resilient research, assuming you do not have bank account in USA or other countries where BTC service coverage is goodJPY => BTC
-international bankwire to MtGox, etc: bank will charge you 5500 JPY.
-fund JPYs with NETELLER/Moneybooker domestic bank wire--> buy VirWox USD --> buy SSL with USD --> buy BTC with SSL. for each conversion you pay commission of 2%~4%.
-buy BTC at amazingly high rate at Youtip: http://www.youtipit.org/faq
currently 1BTC on sale for 27.5200 USD
-buy liberty reserve from crappy Japanese vendors, takes severals days or up to several weeks
if you do have USD bank account in Japan,
-go on forex market, buy USD with JPY, cash out, than international bank wire (which will cost you about 5500 JPY anyway ), fund Gowalla and than MtGox
if you have more than 10000000 JPY in Citibank Japan's bank account, you'll be able to send funds to any bank account in the world for free.BTC => JPY
-cash out with liberty reserve, find someone to have it international bank wire to Japan, absurd handling fee as always
-buy SSL with BTC --> buy USD/other real money with SSL on VirWox --> Paypal --> domestic bank wire
TL;DR: there are no viable option to buy or sell BTC from Japan,unless 5500 JPY is ignorable to you, or you have 10000000 JPY sitting in Citibank Japan's account, or you don't mind losing 10-20% of your asset.
Has anyone had any luck?