This seems to both mess with continuity in terms of there being a "demon" with which a contact can be made, though we'll have to check with Ouro on that, and it doesn't have enough specifics regarding the power of the flames themselves, which is further specified below in the rest of the review.
[hider=review]
Fire Release: Shadow Clone

It seems like something like this would be highly volatile, or at least not very stable as to have a clone constantly be on fire/have burning effect the chakra would have to be constantly emitting. I think you need to add a limited time period for the clone to be on the field because it exhausts its chakra stores.

Demonic Flames, Hellfire Aura, Wind Release: Blazing Twister, and Wind Release: Fire Great Breakthrough

So...how hot are these flames. How much damage would they do to say...a person, or a rock, or a tree, or metal(melted somewhat?) You're not being specific enough. What degree of burn would a person receive from each of these techniques.

Flames of Hell

So what are the properties of this hell fire. You've not gone into any detail regarding that, could you please do so, that way we can figure out what they actually /do/ in comparison to say normal fire, or something like Amateratsu.

Hordes of Hell

I imagine the user would have to remain imobile for this and that it'd be a "one or two" uses per battle kind of thing, correct?[/hider]