4/1/13 Edit: Since the release of the DLC Doritos Crash Course City Lights there have been numerous reports of this achievement failing to unlock. There is no known solution at this time. It is suggested that you get this achievement before purchasing/playing the DLC.There are 5 Japan levels to complete and they aren't accessible until first completing all of the USA and Europe levels. It doesn't matter how quickly or slowly you complete the levels as long as you complete them without skipping forward (or "chickening out") using the RB.
All of the skills you've learned will really be tested in the Japan levels, so be sure to remember all of the following:
1) Sprint using LT or RT.
2) Slide down hills by pointing LS down to build momentum and make higher jumps.
3) Aim for the very center of trampolines and press A right when you hit for the highest jump.
4) Jump off of ropes from the very top for the longest jump.
If you are going for Gold, here are the times you will have to beat:
Level 1: 01:20
Level 2: 01:15
Level 3: 01:45
Level 4: 01:45
Level 5: 01:35