400 years

(3rd person POV)
     "Where is he? That punch wasn't powerful enough to kill him was it?" Natsu thought to himself. He breathed heavily and knelt to the ground exhausted, feeling like he was about to pass out.
     "Natsu! Are you okay?!" The blue cat hovered high above everyone watching.
"Yah little buddy, I'm fine don't worry!" He wasn't necessarily lying but he also wasn't telling the truth. The air was full of smoke and dirt. Zeref's soldiers stood on the side lines unsure of what to do besides wait for their commander to emerge from the crater Natsu had just created.
     "You really have grown stronger...Natsu" The smoke had finally cleared to the point where a black figure with a white toga could be seen, holding his left arm. "Of course, that is to be expected. You've grown up so much." Zeref's expression turned nostalgic compared to the care free expression it was a few seconds ago. Natsu looked up, refusing to give any sign of fatigue.
"Before you decide to use that last attack your foster father gave you and kill me, there's something you should know." Zeref gave a light smile.
     "My name is Zeref Dragneel. I am your older brother."
       The air between them was dead silent. Nobody dared to move. "I suppose I should have told you this sooner, but I wanted to give you the chance go get stronger, to possibly reach the point where you could kill me. I suppose it all started when our parents were killed in a fire. I lost you too and became obsessed with trying to bring back the dead. In the process I created the Etherious and then you," he pauses, "Etherious Natsu Dragneel."
       "Shut up..." Natsu's bangs hung infront of his eyes, his fists clenched.
       "I created you to not only bring you back, but in the hopes that one day you would be strong enough to kill me. I've waited over 400..."
       "I said SHUT THE HELL UP! There's no way I'd ever trust anything you say!" He runs forward engulfed in flames, when he stops a few feet short and nearly collapses to the ground, clutching his heart. The book of E.N.D laid in front of him with Zeref's finger smoking.
       "Didn't Igneel teach you to listen better?"
       "What do you know about Igneel?" Natsu responded through his teeth. Zeref chuckled. "He was a good friend of mine." Natsu's expression turns dark.
       "Igneel told me about his plan to teach you dragon slayer magic. Four other dragons had chosen orphans and had plans to teach them magic as well. You and those four traveled here from 400 years ago through the Eclipse Gate. All this to defeat Acnologia. We needed two celestial spirit wizards to open the gate. A woman named Anna opened it on our end. However, another Celestial wizard opened it up on this side as well. I assume you've heard of her...Layla Heartfilia: the mother of Lucy Heartfilia.
       "YOU'RE LYING, if I'm E.N.D then that means Igneel tried to kill me right?! He could have killed me easily!"             "He didn't kill you because he loved you Natsu. You thought July 7, X777 was the year the dragons disappeared when in reality is was the day you woke up and were sent to this time period."
       So much was going through Natsu's head. Zeref, Fairy Tail's biggest threat, was telling him he was not only his long lost brother, but also E.N.D. He had apparently traveled through the Eclipse Gate 400 years into the future where Lucy's...Lucy. Oh God, was he responsible for Layla's death?!
       "I've already made my choice, I'd rather see the world burn to the ground than have my own death. But maybe you are finally strong enough to prove I'm not immortal...brother."
       Natsu lunged forward, "I AM NOT YOU'RE BROTHER AND I'M NOT E.N.D. My only family is Fairy Tail and you don't want to mess with us!"
       Tears sprung in Zeref's hopeful eyes. Suddenly everything around them seemed to be in slow motion, like in a movie.
       "You are a demon of Zeref, if I die..."
       Natsu was closing in on him.
       "You die too."
       "So what?!" Shock took over Zeref.       "I've already made up my mind just by coming here! I'm not wasting Igneel's power!"
       "This will be the last chance you get to kill me..." Zeref opened his arms waiting...
       "NATSU!" A small voice could be heard approaching quickly. Inches before Natsu could attack Zeref, Happy grabbs him and launches up in the sky.
       "Happy what the hell are you doing?! Put me down!" Natsu struggles against his claws. "This is my last chance before Igneel's power disappears!"
       Tears rolled down Happy's face. "No! I won't let you! What would I do without you? What would the guild do? What would Lucy do?!" Natsu stopped struggling. "Please! I don't want you to die..." That's when Natsu had noticed the small blue paws clinging desperately into his jacket. They were burning...he was hurting his best friend and he was enduring it to save his life.
       Natsu looked away guilt ridden, refusing to make eye contact. He had acted on rage and didn't think about everyone else, not even Lucy. He would never have gotten the chance to tell her...
       "Sorry, Happy. Let's go home..." Igneel's mark began to vanish from Natsus arm; there really was no going back now. They sped off towards the guild, not sure what to tell everyone back at the guild.
       Zeref remained where he was, watching as his baby brother flew away along with his last chance at peace. "Guess you made your choice. There's no stopping me now...Natsu."