Oh sorryYou don't infuse your kunai withfire chakra.
You actually throw the kunais and spew out fire from your mouth to enflame it.
Try again.
Weak point:
Even if the attack is short range, if you throw the kunai, with this jutsu, the fire will douse off after short range, but the kunai will proceed.
Teuchi throws several kunai at the clone. Now Teuchi begins to mould superheated chakra inside his stomach and channels it to his lungs. Now he inhales a lot of air and by channeling his Katon chakra to his mouth, he releases a fireball from his mouth; which inflames the kunai.
Strong Points:
(1). Since this technique is short-range in can be used as a surprise attack considering the fact that it does not require any sort of hand seals or preparation time
(2). If the opponent uses a relatively weak Water technique, the inflamed kunai and the water would collide to create steam which would block the targets view and he would fail to see the kunai moving towards him
Weak Points:
(1). Since the attack is short-ranged, the Fire will douse off after a short time, the kunai however will proceed
(2). Although kunai are usually used to ambush the target, if a fireball is used along with the kunai in order to inflame them; the position of the user will easily be revealed
Combination Strategies:
(1). The kunai can be infused with the user's wind chakra before inflaming it.
Ways To Counter Technique:
(1). A relatively strong Wind Technique can be used to push the kunai back towards the user
(2). Pillars or Walls created by an Earth Technique would quite easily block the technique as the fire would soon die out and the kunai would fail to break through the pillars/walls