Operation Abyss: New Tokyo Legacy

After completing the main game, you have two more "main" missions left to complete. After you complete both, you will have a secondary mission called "Combat Training Exercise". You will fight in the Geomatrix, the same location where you finished the game. The enemies here use level down attacks so have some Level Decoy items in your inventory to avoid this attack. The level down affect is permanent so isn't desirable at all.