I went ahead and finished the game. Turns out you can keep playing after the final battle. You get to create a new save file that is set before the final battle. However, you keep all of the experience and items you gained from that area. When you choose to enter the final battle they don't take you straight to a fight, it's more exploration with random battles and chests to find. Also, after creating the new save file they add more content. I didn't look around but a message popped up mentioning there are some more things to do, including more battles at the Solosseum. I may take a break now and check that stuff out at a later date.