*The Battle Arena appears in Chapter 12.
*It's part of the main story so it's easy to find, you have to fight your way up to Floor 30.
*There are checkpoints every 5 floors.
*There is a burger joint on the main road, in the bridge, for 1500 yen you can have full MP/HP again and try the next floors
*It's a good idea to bring some Kiwami Drinks from the vending machine to get more XP out of each fight.
Recommended level: 30 and up.