I have honestly always preferred a set of steel Sai's when practicing ninjutsu with dual weapons... But I suppose a set of Kama will work if you prefer them. I just like the weight. The set I own weighs in at 5 lbs for each individual Sai. and even though they are used to target pressure points, I find that a sharp tap on the wrist with something as heavy as those will usually make whoever it is drop whatever they are using and dance around for a few minutes complaining about the numbness. ^_^
*DISCLAIMER: I spar with trained opponents who use extra care and caution when we practice together. I DO NOT SUPPORT PEOPLE WHO DO NOT HAVE ANY FORMAL TRAINING EVER ATTEMPTING TO SPAR WITH ANYONE. TRAINED OR NO.