User blog comment:IamJakuhoRaikoben/Chapter 413: The Book of E.N.D, Review./@comment-2214433-20141222172054/@comment-7418318-20141222175646

With the difference that Natsu is known as a hot-headed idiot and Gray is supposedly smart and cool-headed.

And yet it's still Gray who is practically challenging Natsu to a fight, not the other way around... forget the practically, he did outright challenge Natsu to a fight with the words "Just try to take the book from me."