Similiar to most survival horror games, Parasite Eve 2 gives players the option to replay the game with different features. This is really known as a second playthrough, and there are several modes you can different playthrough.

Replay Mode - Clear Normal Game Once
Essentially a replay of the original first playthrough, same difficulty. Aya will start with 10% of average EXP and BP, 100HP / 30MP. All special, extra weapons, armor and items you recieve will be sold at shops at all times.

Bounty Mode - Clear Normal Game Once
Return to a normal difficulty, Golems are plentiful, enemies are even stronger than before. Start off same as the Replay mode exact she will have her EXP and BP cut to 5%. No extra items.

Scavenger Mode - Clear Game With A Mimimum of 69,001 EXP
Basically Hard Difficulty, enemies are harder, Aya's MP is reduced to 10, her starting MP will be slashed to 1% of total average. Shortage of weapons throughout the game. All EXP in game are givven a 5x bonus and a 2-Raml jump in item ranking.

Nightmare Mode - Clear Scavenger Mode
Most difficult gameplay, only for the hardcore.