From the guide on GameFAG:
The PS2 version includes various new gameplay elements not in the original.
1. A brand new opening animation and song (two variations).
2. With the exception of narration and internal thought, the game is fully
3. Additional new characters, new CG, and new bonus extras.
4. Additional new Events and Battle Stages.
5. A new and robust Item system.
6. Eruruu now has a special item technique for various stat/healing/damage
7. Characters now learn unique special abilities and skills.