Getting Gold Fortune Coins:
During the stealth segments, rare coins can be discovered. Octavianus can find one Gold Fortune coin on the final guard in any given location. To obtain it, you must disable every opponent in the given area first. The last man you search (with the Circle button) will yield this rare coin!
Survival Mode:
Get a Silver rank on all the normal events.
Labyrinth Arena:
Get a Silver rank on all the hard events.
Ugly Duck Fling Mini Game:
Get a Bronze rank on all the hard events.
Art Gallery:
Get a Bronze rank on all the normal events.
Armor Upgrade 1:
Earn 300,000 Salvo points by playing through many battles. The points are cumulative. You will be given a strong helmet and arm bracer at the start of every battle from now on.
Armor Upgrade 2:
You will obtain yet another armor upgrade after gaining 800,000 Salvo points.