Ok here is my 2 cents. this is a Genjutsu Dojutsu. I do not belive that it should be based on Fire Affinity but Jutsu Power. This is a illusion not flame. Second I remember that episode and I don't beleive that Itachi took any damage for it like his summonings so I would tend to belive that the -30% HP should not be there. Third, I belive that there should be a penently to speed on the target after this to represent the struggle that had just happened. This should also not be curable unless said shinobi has a med-nin present with the Jutsu to heal or he spends time in the hospital.
Ok I would like to request that you limit it's aviablitiy. I here you screaming already but here me out. The Mangekyo Sharingan seems able to be gotten from a couple of different ways, so all should find a way that suit them. However I have noticed that each user had some Unquie abilities that the others did not, the only ones I know of that shared some abilities were Itachi and Sasuke. Tobi could have had or seen some of them devolping in his clan but it seems each person is different in their abilitly with it. I am not saying only one person but maybe only 4 or 5. Unfortunetly, the clan was wiped before it could be fully gotten into. Ok remember you can take the request with a grain of salt and throw it out if you chose too. But other than that I think you had it pretty well.
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I am willing to battle to the Death, but both sides must agree. If you are looking for some to win, i.e. Byakugan, it must be stated in your first post. Remember an Eye for an Eye, because I will also ask something of you as well.
If you need any help, let me know and I will do my best.
Je parle un peu français et je suis prêt à vous aider si cela est votre langue primaire.