You can create autorun pathways while exploring dungeons. Use this to create a closed loop that makes your party run around infinitely, until you stop them. While your party is running around in circles, they will encounter enemies. When holding A, you will rapidly select attack (melee). Get something to clamp down A, and you will be able to fight monsters while the game is idle. When you return, you will have gained experience. The amount of experience is directly proportional to the amount of time you let your party run around, how much experience the monsters are worth, and the rate of encounters. Note: Make sure your party is strong enough to survive each encounter, and have a healer.
Etrian Odyssey 4: Legends Of The Titan