- #122
If Zeref is Natsu's biological brother,I wouldn't be surprised if Acnologia too was trained by Igneel in dragon slaying. That would explain why Igneel wanted to kill him himself so much.
That would also make Acnologia Natsu's brother disciple,just like Gray and Lyon.
The other possible explanation was because E.N.D was a child and Igneel couldn't bring himself to finish him off. Instead,he opted to adopt him and give him a clean slate.
Knowing Mashima,he prefers to keep things simple,so I doubt there was any de-aging involved when he adopted Natsu. Zeref mentioned that Natsu has grown as well,so yeah,he was a kid when he fought Igneel and almost beat him.
This also explains why Mard and Tartarus didn't recognize Natsu and how Natsu was able to grow up despite being an etherious. It also partly explains why the guild is called tartarus,since Mard Geer Tartarus was more or less the regent there. E.N.D was the guild master,but Mard geer was the administrator.
This should also finally prove that Natsu is E.N.D . There are some obtuse people who still doubt it or who think he is an evil counterpart or something of the sort.
What's most peculiar is Zeref's curse. I wonder about the being or thing that cursed Zeref. I wouldn't be surprised if it upstaged Zeref and Acnologia later on as the manga's main antagonist.