After successfully completing a mission, you can switch to "Shadow Mode" by pressing the Start button at the Story Mode - Mission Select screen. This allows you to play a more difficult version of the missions you have already completed with less items and more enemies in different configurations.

To unlock the following four items, collect map pieces and beat the assignments a and missions described for the desired effect.

Finish all 50 trainings with an S Rank. This will add the Colored Rice to your inventory.

Acquiring S rank per mission in story mode unlocks 4 additional assignments. This unlocks all possible extra assignments per one mission in story mode. Obtaining A rank will grant 3 of the extra 4 assignments. Finally achieving B rank will give 2 of the 4 extra assignments.