Operation Babel: New Tokyo Legacy

As you progress through the story, the Encounter Gauge will be unlocked. The Encounter Gauge goes from Lvl. 0 to Lvl. 6. As you win battles, the Encounter Gauge increases slowly and eventually levels up. At higher levels, enemies are stronger and continuous encounters are more frequent. The Encounter Gauge stays the same when you leave a dungeon. When you run from a battle, the Encounter Gauge decreases by one level. The Encounter Gauge also lowers whenever you defeat an area's Wanted Variant for the first time, and it fully empties if you get wiped out. You need to win 30 battles while the Encounter Gauge is at max without the gauge getting lowered. The 30 battles do not have to be in the same dungeon, so you can always leave, heal, and return. Likely you'll get this naturally if you're level grinding, but if not, you can always return to an easy dungeon and defeat everything you see. Use the Academic's spell Neo Chain for more frequent encounters.