Improved Two-Weapon Fighting (Combat)
You are skilled at fighting with two weapons.
Prerequisites: Dex 17, Two-Weapon Fighting, base attack bonus +6.
Benefit: In addition to the standard single extra attack you get with an off-hand weapon, you get a second attack with it, albeit at a –5 penalty.
Normal: Without this feat, you can only get a single extra attack with an off-hand weapon.
It says an off-hand weapon. A kasatha has three off-hands, therefore as I read it has one extra attack with each off-handweapon if he takes this feat.