User blog comment:IamJakuhoRaikoben/Chapter 451: Fairy Heart, Review./@comment-4449950-20150907045807/@comment-5303512-20150907053121

I am glad we found a conclusion to the backstory chapters, so now Fairy Heart is Infinite Magic. Wow! That is something you don't see everyday in Fairy Tail

@Jaku & Carrot, Well Natsu has been training for a whole year so of course he has to develope new techniques to defeat powerful enemies, there are two possibilities of what this technique might be linked to.

1. also he is E.N.D. (which is part of my theory about him just having the body of the demon while his consciousness is sealed in the book.) maybe this is one of E.N.D.'s techniques in order to beat Zeref.

2. A new form of Dragon Force which his body becomes to the transformation of a Dragon (hint to the promo pic for the Fairy Tail Movie 2) in order to beat Acnologia but will have to use it early.

Although it makes me wonder, with him reacting so anxiously to the Spriggan 12 members, will he be forced to use it prior to his battle with Zeref?

Another theory I have is he will come to understand his origins and awaken the true powers of E.N.D. When he is released from the book in order to beat Zeref and Acnologia.