Completion bonus - Successfully complete the game to unlock the "New Game+" option. While entering a battle in the New Game +, hold L1 to hear music from the original Valkyrie Profile. While entering a battle in the New Game +, hold L2 to hear random music.

Easy experience - After defeating the Ballistic Rhino at the end of Royal Underground Path, you can fight it repeatedly. When prompted, go into the altar. You only get 1600+ experience points and 290 OTH, but you can also get a Baraka (an accessory that increases a character's HP).

Successfully complete the game, then start a new game. The new game will increase in difficulty, depending on the amount of times the game has been previously been completed. This is indicated by the number and size of the crystals that appear on the main screen.

Two player mode - To play along with a partner in the battles, press Select to go to the menu, then go to "Party configuration". In the box where you can change the characters position, press Triangle on the character you want player two to control.

Unlockables

Hard Mode  -  Finish the game to make any New Game playthroughs harder. The current difficult level is represented by crystals on the main screen. Every game clear adds one crystal, and 10 crystals will become a big one. The max is 5 big crystals (difficulty increased 50 times).

Random BGM during battles - After you beat the game once, hold L2 while entering battle

Secret Dungeon - Save the game at the last save point to unlock the Seraphic Gate on the world map. This secret dungeon has new characters, items and powerful enemies to be found. Once you beat it you can enter it again and the enemies will have gotten even stronger!

Seraphic Gate Save at the last save point

Extra Characters - Characters unlocked in the Seraphic Gate (SG).

Dylan Defeat Gabriel Celestia on floor 1 of the SG
Freya Defeat Freya on floor 4 of the SG
Hrist Defeat Woden on floor 2 of the SG
Lenneth Defeat Woden on floor 2 of the SG
Leone Defeat Gabriel Celestia on floor 1 of the SG
Lezard Defeat Obsessed Ex on floor 3 of the SG
Silmeria Defeat Woden on floor 2 of the SG
Valkyrie Defeat Ethereal Queen on floor five of the SG

Valkyrie Profile 1 Battle Music - In New Game + just hold L1 while entering a battle