Swimsuits
Once your done clearing Absorption Gate Complete the Rappig Hunt sidequest in Grand Cokhma to get the spa pass. Go to the Keterburg Hotel and use the spa to get the costumes.
Final Battle
After viewing the last scene in Eldrant Talk to Peony in the throne room.
Abyssman
once your on the 2nd playthrough and have cleared Absorption Gate Talk to the maid in Peony's chamber to get the Abyssman costumes.
