(Katon: Hōsenka no Jutsu) - Fire Release: Phoenix Sage Fire Technique
*I begin by memorizing the necessary handseals before lining my insides with a protective layer of chakra. Afterwards I knead more chakra and channel it to my lungs. When I feel that I've molded enough chakra, I begin to heat it up and initiate the nature transformation. After a little while longer, I perform the necessary handseals, evenly divide all of my gathered chakra, and release multiple fireballs in the direction of your first clone. Some of the fireballs are aimed directly at him while the others are purposefully aimed within his general vicinity. The reason for this is to cut off his means escape -- if he tries to avoid the fireballs coming directly, he'll end up moving into the path of the fireballs that were initially aimed to miss him. If he doesn't try to avoid and instead tries to defend against the fireballs coming directly at him, then I'll manipulate the remaining fireballs so that they'll all converge on him from his sides. With no where left for him to go, your clone is inevitably pelted fireballs and dissipates.*
Advantages: This technique is versatile in that it can be applied in multiple ways. Because you can manipulate the fireballs and alter their trajectories at your whim, it makes avoiding the fireballs difficult. Furthermore you can conceal shuriken within the presence of the fireballs and manipulate those in a similar way to the fireballs, making it even harder to avoid. As it says in the description, because of the way this technique occupies the opponents attention, it can be used as a distraction to raise the chances of the a successful follow up attack.
Disadvantages: Since it seems that this technique is --for the most part -- used as a distraction, I assume that it's never used with the intent to deliver the final blow. Even if it did hit, it doesn't seem like the damage dealt would be anything serious enough to prevent someone from continuing a fight.
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(Katon: Honoo no Saigai Hi Kagayaku no Jutsu) - Fire Release: Flame of Disaster Fire Shine Technique
*I begin by forming a protective layer of chakra to coat my insides, then I begin to knead chakra and channel it to my lungs. After a little while, when I've molded enough chakra, I begin to heat it up and initiate the nature transformation. When the moment is right I exhale the chakra which ignites externally as a mass of fire. I proceed to issue mental commands to my chakra and manipulate the fire to converge on your clones position; even if he tries to avoid, the flames will chase him down. With no where to go, the flames wrap around and consume your second clone.*
Advantages: Because of the way the flames are manipulated to converge on and wrap around their target, it leads me to believe that the user is able to exert their will over the flames even after releasing them. Similar to the previous technique, it seems like you might be able to will the flames to chase after a moving opponent, which would make it difficult to avoid. I'm not entirely sure about this though, so please correct me if I'm wrong.
Disadvantages: Ultimately doesn't seem all that powerful nor hard to defend against, though I'm not sure you'll consider this a real disadvantage.