Is there a "traditional japanese way" of attacking with a knife?
You'd have to ask an exponent of something like Takenouchi Ryu, Shindo Yoshin Ryu, or Araki Ryu. If only there were such people around here.
I am sure Aikido knifework looks nothing at all like the way those systems teach how to handle a knife. Though you could say that the way we attack is like a desperate, last-ditch kamikaze attempt to punch through armor on a battlefield, its definitely not the savvy, sneaky knifework of a predator.