So I've finally finished playing Afro Samurai.  I'm taking it to GameStop tomorrow so unless some new DLC comes out I will not play this game again.  What caused me to pick up the game again was to finish of a couple of the achievements I was close to completing.  On each level there are mementos scattered around the levels for you to collect.   On the map they are shown as a group of crows gathered together.  Most of the time they are off to the side and reward those that are willing to look around in the level.

The secrete bonus to finding these mementos is they open up additional combos.  Each level contains five mementos and most are very easy to find if you just take a look.  I found most on my second time though the game but resorted to a game guide to get the last couple.  The only issue I found was that if you start a new game you lose all level progression so be aware if you want to run through the levels to pickup more mementos you won't want to start a new game.