After successfully retrieving Makarov from the Alvarez Empire with little resistance due to Meliodas' interference, the now reunited Fairy Tail guild assembled in their building back in Magnolia Town.
"Dammit! What do you mean Meliodas ran in by himself?" Natsu exclaimed. "If I had known that, I would have gone after him!"
"And that is why I DIDN'T tell you until now." Makarov said. "The Spriggan 12 are not people to be messed with like that. He's gotten even stronger but he was dealt with. His magic suddenly disappeared."
"Well there's no way he's dead!" Natsu shouted.
"I don't think he would have died that easily. They must have done something else." Erza commented.
"You think he was sealed away?" Lucy asked.
"I doubt it." Gray chimed in. "He broke out of my Ice Devil Slayer magic easily, and it's something that was made specifically for demons like him."
"Well whatever happened to him, we just have to assume he's alive and somewhere. Mavis said. "But since we don't know his whereabouts, we'll have to continue without him. I trust we'll see him again very soon."
"In the meantime, we'll have to stop Zeref's forces from invading without him." Makarov said.
"So how do we deal with an immortal like Zeref?" Freed asked.
Don't worry about him, I'll take care of Zeref. Natsu replied, standing in the corner.
"And how would you do that Natsu?" Erza questioned. She observed Natsu, who seemed much different from before.
"I've been training with Meliodas fire technique. It has the ability to burn his immortality." Natsu replied calmly.
"Wait…you don't mean-" Gray remembered Natsu and Meliodas both fighting Zeref, with Natsu having eaten Meliodas' hellblaze. "You still have access to that power?"
Natsu nodded his head in agreement.
"What power is he talking about?" Lucy asked. She looked to Happy but Happy remained silent, with a worried look on his face.
"Uh…Happy? Are you alright?"
"Aye…" Happy responded, taking one more look at Natsu.
"Meliodas gave Hellblaze to Natsu to fight Mard Geer. Then Zeref showed up briefly and the two of them fought him. When Meliodas managed to land an attack with his sword covered in Hellblaze, the wound didn't heal."
"Oh that? Yeah I still got the nasty scar on my chest from when I fought him and he lowered the intensity of it when he did cut me." Laxus added.
"Flames that can stop even an immortal from regenerating…" Mavis looked at Natsu. 'Maybe you can free us from the curse…'
—
Half a day passed, with the Fairy Tail members resting in their houses, waiting and anticipating the inevitable war.
Natsu lay asleep on Lucy's bed as Lucy sat with Happy.
"What was going on with you earlier, Happy? You didn't seem like yourself when they started talking about Natsu's new power."
"Aye…it was when we went to train for a year…Natsu started training with those black flames, but the more he used it, something became…different about him…" Happy responded.
"Different?" Lucy glanced over at Natsu on her bed. "Yeah he did seem a bit…off. He's not as loud as before."
"Well, he would sometimes just suddenly space out then snap back to reality like nothing happened. I think I even heard him say Zeref's name in his sleep once or twice…And then we ran into Gildarts and he used those flames again to fight him…" Happy's eyes began to tear up. Lucy immediately grabbed Happy closer to her and hugged him.
"He wasn't Natsu anymore! Gildarts had to use his full power to knock him out! But in the process, Gildarts' arm was completely incinerated!" Happy cried out.
"He's missing both his arms now?!" Lucy exclaimed.
"No. It was his prosthetic." Happy responded.
"So that's why you're afraid of Natsu using that. Well, Meliodas was the one who gave Natsu that power, so maybe he knows a way to-"
Warren's voice suddenly echoed in all of their minds, causing Natsu to immediately jump out of bed.
"WE HAVE MULTIPLE LARGE MAGICAL SIGNATURES RIGHT OUTSIDE OF MAGNOLIA TOWN! EVERYONE IS TO MEET AT THE GUILD IMMEDIATELY!"
Out of the corner of Lucy's eye, she noticed Natsu had already started climbing out of her window.
"I have a door you know!" Lucy shouted as she and Happy followed after him.
—
Natsu, Lucy, and Happy ran towards the guild building. On their way, they noticed the ships charging their magic cannons.
"We're not gonna make it!" Happy shouted.
"It's fine! Master anticipated this and had Freed set up a barrier." Lucy responded. Moments later, hundreds of magical cannons fired, only for their blasts to be stopped short of the town by a transparent dome of magic.
The group continued running, meeting up with Mavis and the rest of the guild in front of the guild.
"Master Mavis, which plan set are we going with?" Erza asked.
"Set A. We'll have the dragon slayers-" Mavis paused as she noticed Natsu was not paying attention and glaring at the ships.
"Natsu pay attention!" Erza shouted.
Happy looked into Natsu's eyes and immediately recognized his facial expression.
"It's happening again…" Happy mumbled.
"URAUUGGHHH!" Natsu screamed, his magical power flaring up massively and blowing back the guild members behind him.
"HELLBLAZE DRAGON MODE!"
"That magical power!" Makarov exclaimed.
"This is unexpected, but it will work in our favor. Warren, tell Freed to lower the barrier!" Mavis shouted.
"Alright!" Warren put his finger tips on his head as he began to telepathically send Freed a message.
"HELLBLAZE DRAGON ROAR!"
Natsu took a deep breath in, and let out a large ray of black flames from his mouth.
"Shit! Freed's not gonna be able to lower it in time!" Warren exclaimed.
The flames collided with the barrier, shattering it immediately with no resistance and Natsu swept the ray across the sky, engulfing every airship above Magnolia in black flames. The sky was lit ablaze with huge explosions, with no traces of any of the ships remaining or any debris making it to the ground. The guild was silent at the display of power Natsu had just performed.
Natsu remained still, staring up at the smoke lingering in the sky.
"Zeref…" He mumbled.
Natsu suddenly leaped up into the air, with black flames erupting from his feet as he made his way west.
"Natsu…he's really lost it this time…" Happy said with tears forming in his eyes.
"Then it looks like we're going after him!" Lucy said.
"I'll come with you. You'll need an Ice Devil Slayer to deal with the flames of a demon!" Gray interjected. "Shouldn't be a problem right Master Mavis?"
Mavis shook her head.
"This goes a bit out of plan, but it worked in our favor since we only have the ground troops to deal with. We'll continue with set A and we'll leave Natsu to Lucy, Gray and Happy!"
—
Western Fiore
"Your Majesty. It would appear an incredibly fast object is approaching us. And this magical power…" Invel said.
A smile formed on Zeref's face.
"Your Majesty?" Invel looked at Zeref with surprise.
"I know who it is. Let him come. Or perhaps I should greet him myself-" Zeref's eyes widened as Natsu landed on the ground in front him. Behind Natsu, the entire land was burnt to ashes by roaring black flames.
"YOUR MAJESTY! OVER 700,000 TROOPS WERE KILLED! GET AWAY FROM HIM!" Invel jumped in front of Zeref and raised his right hand out.
"Ice Slave!"
A collar of ice formed around Natsu's neck. Steam began to erupt from around Natsu's neck immediately as the collar began to melt.
"I see…" Zeref said. "You've progressed far faster than anticipated, Natsu."
Invel continued to stare at Natsu but Natsu only kept his fixation on Zeref.
"So this…this has to be END correct your-"
Natsu suddenly leaped forward at Invel, throwing a punch straight through Invel's chest in an attempt to reach Zeref.
"Natsu…as much as I want to fight you, come find me instead." Zeref surrounded himself in a black orb before disappearing.
"GGhhhghh! Y-your Majesty…" Invel grunted as blood dripped down his mouth.
"I will not let you kill his Majesty!" Invel shouted and grabbed onto Natsu, the skin on his hands burning down to the bone.
"True Ice Kamui!" Invel surrounded both himself and Natsu in ice, encasing the two of them in a massive crystal that towered over the mountains.
Silence passed for a few moments. A crack formed in the crystal of ice that split down the middle with black flames leaking out. The crystal suddenly shattered as black flames erupted in every direction, melting the very land beneath their feet. The forest around them turned into ash and the mountains nearby melted into large pools of magma.
Only Natsu remained standing in the blackened crater, with no trace of Invel's remains anywhere. He maintained the same empty stare as before.
"Zeref…" Natsu trudged along the barren landscape making his way back east.
Walking mindlessly in one direction for a few hours, Natsu paused as he saw three familiar figures running towards him.
"Natsu!" Happy cried out.
"Dammit flame brain what's gotten into you!" Gray shouted.
"This heat…" Lucy said as the three of them stopped. They could not get any closer to Natsu due to the immense heat coming from his body.
"Zeref…" Natsu continued walking forward, paying no more attention to the three of them.
Lucy and Happy stepped away from Natsu due to the heat. Gray's hair began to rise and a black marking formed on his right arm. He placed his hand on Natsu's shoulder.
"If you don't stop, I'm gonna make you stop." Gray said firmly. Natsu stopped walking and turned his head to look at Gray, locking eyes with him.
"Gray…"