Omigosh why have I never discovered the existence of this. This is supposedly set approximately after the battle against Lust in episode 20 of FMAB. Well its only put there because if you watch the anime, you'll know that you can't have anything before or after the series heh, it has no impact whatsoever on the plot of anime. Personally I feel it would still probably be a good idea to watch FMAB first before watching this though.
ITS SOME EPIC STUFF.
I'm a happy fanboy \o/.