Whenever you're in a battle you can go back to get more experience later. This way you are able to get unlimited experience.

Cheat Mode:
To enter Cheat Mode, select the "Code Entry" option on the "Extras" menu to enter one of the following cheats.

Double Damage:
34743

Unlimited Stealth:
53467

Unlimited Copper:
23637

Unlimited Chi:
24463

Unlimited Health:
94677

One Hit Dishonor:
54641

Character Concept Gallery:
97831

All treasure Maps:
37417