Refresh for each blue chest and take appropriate reward:

If Enemy shows up, he takes away:

If Rival shows up, he takes away:

If Both show up, use Rival!

If Prize is 2 items:

Blue Chest: remedy, potion, 10 gil, 24 EXP

If Prize is 4 Materia:

Blue Chest: blue, black, white, red, 05 gil, 33 EXP

If Prize is 2 AB Letters:

Blue Chest: letter06, letter05, 10 gil, 26 EXP