On your account, change your Locale to japan, by going to system settings

then go to bing and search for "Monster hunter", Click on the one that says "Monster hunter: frontier [japanese letters]"

and then download it the demo ( this demo gives you the codes )

after you start the demo click the bar in the middle of the screen and you should find two codes, one above each other, in a [xxxxx-xxxxx-xxxxx-xxxxx-xxxxx]format.

One should say something in japanese before the code, you can tell which one it is because you can see the number "48" within the writing

Copy the code and redeem it on the account you wish, itll say you have limited xbox live time, it gives you 2 weeks to play on live and join parties.

you get 1 code per account, so you will need to make new xbox live silver accounts to get new codes, you can make fake information on the account.