See the rules in OA for using Iaijutsu Focus in combat. Essentially if you get the drop on your opponent, and you draw your weapon in the same round you strike, you get to do juicy amounts of extra damage.
Iaijutsu Focus also has one other great advantage IMO: it gives tanks an incentive to put points in Cha, which would otherwise be a dump stat.
Iaijutsu Focus also has one other great advantage IMO: it gives tanks an incentive to put points in Cha, which would otherwise be a dump stat.