Can you use bitcoin to transfer money from US to Japan and what would it cost for approximately $10,000 usd?
Bitcoin doesn't know countries. If you want to have 10'000 USD exchanged for Japanese yen, you can buy 17.42 BTC on a US bitcoin exchange, transfer the money to the account of a Japanese bitcoin exchange typically for free (since you can send the money in BTC from one exchange directly to another one and both typically doesn't have costs attached), and exchange the 17.42 BTC for Japanese yen on a Japanese BTC exchange.
Both exchanges will probably take about 1% of the money exchanged in fees, so it's still really expensive unless you find exchanges with low fees or constant fees regardless of the amount of money exchanged (so the costs don't scale with your rather large amount of money).
You can find bitcoin exchanges here or simply by googling.