Mailing from Japan to US

Can I use US stamps to mail Christmas cards& letters from Japan to US or do I need to get Japanese postage.

Where can I buy Japan postage, must I go to the Post Office or is it available at other places?

Is it the same as in the US, a 41cent stamp is sufficient for mailing regular size envelopes.

Can I use US stamps to mail Christmas cards& letters from Japan to US or do I need to get Japanese postage.

You need the postage of the country you are mailing from. If you are in Japan you need Japanese postage.

Where can I buy Japan postage, must I go to the Post Office or is it available at other places?

Post Office

Is it the same as in the US, a 41cent stamp is sufficient for mailing regular size envelopes.

No. Depends on weight, but a 50g letter is 90 yen domestic and 190 yen international.

Check here for rates:

http://www.jetsetjapan.com/infozone-daily-post.shtml

http://www.post.japanpost.jp/english/

You can also buy stamps at most convenience stores but they may not know the appropriate postage for the article you are sending.

A standard letter, i.e. one with just one or two sheets of paper, is 80 yen inside Japan and 110 yen to overseas- yllwsmrf gives rates for a slightly heavier one.

You need Japanese Postage.

If you are in doubt about how much something might cost to mail, take it to the post office, they'll weight it and tell you how much it will cost to mail.