User blog comment:IamJakuhoRaikoben/Chapter 337: The Golden Plains, Review./@comment-4449950-20130628130250/@comment-4829046-20130628133839

I think Mashima uses their relationship as a joke really. Then again, Haru showed the "beyond" just-friends thing only after Lucia kissed Ellie, until then it wasn't really true love that he felt. It began to develop more and more after that.

Same thing could happen here, but Natsu is denser than Haru so...