There are two ways to unlock this Trophy, but both involve launching the game and pushing the Touch Pad to open the Options menu.
Once inside the Options Menu, you can either:
-- A. Scroll down and select "Game Reset," or...
-- B. Scroll to "Game Settings" and then select "Restore scores and rankings"
Either method works, but Option A is slightly faster.
Also, if you're getting the Japanese-language version of the Trophy text, it translates to:
Game Reset (15)
The game has been reset.