During plot: You’ll earn plot points, as well as one item from a special prize pool.
After plot: It depends on the difficulty! Easy Mode will earn you 500 NP and one item from a prize pool, Medium Mode will give you 1000 NP and a prize from a slightly bigger prize pool, and Hard Mode will grant you 2500 NP and one item from an even bigger prize pool – with a chance at winning something really rare!