There are no further difficulty trophies. If you desire a little bit more challenge, then start on Normal. Enemies are very easy and the game is relatively forgiving.
Feel free to play on Easy once you follow the instructions above and gotten 'Our Little Secret'. Step 2 : Start up a new game on Easy or Normal. That's the only difficulty trophy and here after you can choose to continue on Easy or restart and play on Normal if you prefer a challenge. Step 1: It is recommended that you start the game on Normal difficulty, then press and choose to lower the difficulty to Easy to get the ' Our Little Secret ' trophy out of the way.