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: elixir, aqua, 05 gil, 25 EXP

If Prize is 4 Materia:

Blue Chest: blue, red, blue, blue, 20 gil, 17 EXP

If Prize is 2 AB Letters:

Blue Chest: letter03, letter04, 05 gil, 18 EXP