After completeing the game, choose to save your file and the game will reset on its own. The next time you go to the title screen, a new feature will be open, the Extra Menu. You can view a photo gallery, cards, the music in the game and other things.
Shurelia's Cosmosphere
During Phase 3 recruit Shurelia and make sure both Misha and Aurica's Cosmospheres have been completed through Level 7. Rest at an inn and talk to Shurelia and the next time you go to a dive shop you will have the option of diving into Shurelia.