User blog comment:Miskos3/Fairy Tail 535: The Greatest Power, Review/@comment-7418318-20170512131719

Hmm... so flames, potentially demonic ones, are entering Lucy? I wonder if the E.L.H. joke I made last week might really happen after all. Imagine that... Natsu's demonic side wandering off into Lucy.

At first I thought Natsu knew what happened when he said his thanks to Lucy, but then he had to go on with Happy... I guess that means he has no clue what Lucy (and to a lesser degree Gray) did for him and this was just for showing him friendship in the past...

But even so it is interesting that he mentioned Lucy ahead of Happy in this context.