Moe Chronicle

"Job Panties" are new outfits for the monster girls that change their stats and abilities. You can find them in one-time treasure chests, and randomly at item harvesting spots in the dungeon when the marker displays a pair of panties as you approach. There is also one Job Pantie for each girl that can only be obtained as a rare drop from defeating monsters, indicated by a heart with a "?" above the monster. There are 150 Job Panties to collect in all (3 alternate costumes for each of the 50 monster girls). This will require some grinding and will probably be one of the last trophies you unlock.

Arrawnt on the GameFAQs forum has created a spreadsheet showing all the Job Pantie locations.