Wow didn’t see this coming. I don’t know what’s going to happen but I can say I am definitely glad Mashima made Natsu at least have some form of awareness. He knew that Dimaria was an enemy and Lucy was someone he held dear to him and I think his instinct overcame his demonic urges and knew he had to save her at any cost (also shown when he bumped into Gray and recognized him). But did anyone notice he didn’t kill Dimaria? I think personally a piece of Natsu is telling him not to kill despite now becoming an un-stoppable killing machine that is hellbent to kill Zeref. I think the lovable flaming goofball we all know and love is still in there and forcing the demon that is now showing to not hurt anyone he cares about.