Smoke is an advanced ninjutsu that encompasses chakra enhanced smoke that can be used mainly as smokescreens, for tactical means, or even offensively to choke a target out. It is strong against fire, choking out the element, while being less effective against wind as well as earth. It can also be used along with tools that produce the source, giving the user more flexibility during combat.
Closing my eyes I taken in a deep breath as I focus while surging my smoke chakra throughout my body. While doing so I think on the properties of smoke. Light, filled with particles, free flowing, etc., and keeping my body in mind I begin to translate the properties of smoke to it, and thus, I become a body of smoke rooted to the ground. Whoa!
I would then take out a kunai with my hand that I make denser than the rest of my body before stabbing myself in the torso, which remains less dense, and thus, the kunai phases into my torso without dealing damage.