New Game+:
Successfully complete the game to unlock the New Game+ option. This allows you to start as Kharg with a King Statuette, 999 Spirit Stones, 3 Diamond Coatings, and 100,000 G; or Darc with a Romantic Stone, 999 Spirit Stones, 3 Diamond Coatings, 10 Bountiful Fruit, 50 Dilzweld Bombs, and 100,000 G.
Secret Characters:
Diekbeck: When controlling Kharg's party beat the 30 round Arena trial in Cathena to get Diekbeck
Choco: When controlling Darc's party beat the 30 round arena trial in Rueloon to get Choco