UPDATED:
Not my video, but explains the steps for those who don't like to read.


Steps:
1) Be signed into any online account.
2) Head to Console settings and language and Locale settings.
3) Choose Locale and choose Japan which would dissconnect
4) Now go back onto your online/offline account.
5) Sign out and When your signed in click Create account (Use the xbox home button on controller)
6) Create the account with any email like Chucky @ love.com
7) Then pick any question and add anything (5 Letters +)
8) Once you've done this it should bring you to deals within Xbox Live
9) Skip these deals and the alternate email address by pressing (x).
10) On the xbox dashboard you should go accross to the home Tab.
11) On the home tab scroll accross the advertisements untill you find
'Monster Hunter Frontier 4' by using (RS)
12) Click the ad then once opened click the first image
(Should ask to download)
13) Download the *FREE* game
14)play the game
15) choose the red bar and underneath it should say "click"
16)Use the top code like in the picture
17) sign in all accounts and write down the codes and redeem them.
(You can only recieve one 48 hour trial per account. Hurry! Before it gets patched!)