I don't own anything, I'm only doing this because I am bored, again, and got nothing else better to do. Everything belongs to their respective owners.

I should probably explain a few thing so you guys can understand what is going on in this. In this, Natsu knows that he's E.N.D and has all his powers, memories and true demon form. However, he is keeping it hidden. Zeref thinks he and Igneel had sealed him away, but he only pretended to be sealed, thinking that Natsu is just, well, Natsu. Natsu/E.N.D has use his power to make it appear that his book is real, when in reality, it's just an solid illusion. This is why Tartaros is unaware that he's always been free.

Moving on to what happening in this made up story itself, Gray said something that made Juvia sad, and she ran until she bumped into Natsu. She cried and told him what happened, believing that she was at fault, and Natsu just decided to not hide his true self anymore and teach Gray a lesson, while showing everyone else what he really is.

This has a tiny bit crossover because of the origins of E.N.D and his power and form, you might recognize it, or not. Anyway, check this out. A tiny bit of Natsu x Juvia if you look closely. You can also tell that there's some Undertale references here.

Natsu was just on his way from his house to head to the guild. Happy had already gone to the guild earlier, and the reason Natsu hadn't gone with him then was because he was still asleep at the time. It was pouring down rain, but he didn't mind it at all. He like the rain, even though he doesn't know why, he just does. It also reminds him of Juvia, since she can control water and make it rain.

Anyway, he was almost to the guild when he bumped into someone. After recovering from the collision, he saw that he ran into Juvia, and she was crying.

"Juvia?" Natsu asked the water mage.

Hearing him talking to her, Juvia looked at him.

"Natsu-san?" Juvia question as well.

"Are you alright?" Natsu asked.

Realizing that she was still crying, she tried to wipe away the tears, but to no valid.

"It's okay Natsu-san, Juvia is fine." Juvia told him, but her tears and cracked voice told Natsu otherwise.

"Juvia, what's wrong?" Natsu asked again, after helping her get off the ground.

The water mage trembled a bit, more tears were coming down her face. Natsu didn't like seeing her sad. It made him feel sad, and angry as well because someone might have made Juvia cry.

"Come on," Natsu said as he grabbed her hand, "Were gonna head back to my house, then you can explain what happened." he finished as he begin to take her to his home.

Juvia was a bit confused, they really never talked much, and yet he's worried about her. She didn't have much time to think about it as they arrived at his house, which was a lot cleaner than she thought it would. Taking her to sit on the couch, he began to asked her again.

"Juvia, why are you crying?" Natsu asked her softly, not wanting to rile her up. "You being like this isn't you."

More tears began to come down her face. As she trembled, Natsu wrapped her into a hug, surprising the girl, before letting her tears flow. She began to tell him what happened.

"J-Juvia was at the g-guild when G-Gray-sama came in. It was r-raining when he arrive, and he didn't like it. H-He thought I was making it rain, and he voiced out that Juvia w-was being annoying by m-making it r-rain." She manage to get out, before crying more into Natsu's embrace.

Natsu, on the other hand, was feeling furious. He understood why the rain picked up on his way to the guild. It was raining naturally, and yet Gray blamed it on her. All because he got annoyed by getting wet by the rain. He notice that Juvia had fallen asleep from crying too much, so he took her to his room to place her in his bed. He took of his scarf, placing it on her neck to help keep her warm.

Many thought were running through his head. How could Gray be so heartless, he knows how the rain made her feel, and yet he hurt her feelings anyway. Natsu decided, no more hiding, no more of this happy go lucky facade, everyone will know the real him and Gray will feel pain. He hurt her, and now he'll hurt him with his true strength.

'MEANWHILE AT THE GUILD'

The guild was being itself like always, people fighting, people drinking, you know, the usual. Currently we see Lucy, Levy, Gray, and Erza at the bar. They got on Gray about how the way he acted, and told him that when Juvia comes back to the guild, he must apologized. Gray, who didn't want to feel their wrath, especially Erza's, he agreed.

Just then, the door opened to reveal Natsu, who slowly walked into the guild, his hair casting a shadow over his eyes.

"Natsu, where have you been?" Lucy question, knowing that he should have been at the guild a while ago. Though Natsu didn't answer her, not to be mean, but because he had something else on his mind.

"Gray." Natsu said getting his, and everyone else's attention.

"What do you want flamebrain?" Gray asked, stand up from his seat.

Natsu, who's hair is still casting a shadow over his eyes, asked him, "Is their a reason that you decided to hurt Juvia's feeling?"

If everyone wasn't paying as much attention before, they are now with him bringing Juvia up and all.

"I know, I was a jerk I get it, I'm planning to apologize when she comes back to the guild flamebrain." Gray answered, thinking, along with everyone else, that Natsu will now just insult Gray back, and then battle it out like always.

But to their surprise, Natsu just chuckled, before replying to him, "Really, you think I'm gonna just let it go because of that? you hurt her, and you expect me to just accepted that excuse!?" Natsu started soft before raising his voice at the end.

"Natsu, Gray understands that what he did was wrong, and he's gonna fix it when she comes back." Erza told him, "Calm down."

"That's not good enough." Natsu answered, as suddenly everyone felt a huge magical surge coming from Natsu. "That's not a good punishment for what he did, he hurt her, and now I'm gonna hurt him."

"Listen you idiot, I know I was wrong, you don't have to get so worked up about it. Its not like you can beat me anyway." Gray said, since they are rivals, this kind of talk was normal for them.

But then, Natsu lift his head, everyone can see his eyes now, and what they saw scared them, even Erza. His eyes were glowing green, they never saw Natsu do something like this before.

"well the, guess then I should hold back no longer." Natsu replied, and he was suddenly envelope by green flame before they died down, allowing everyone to see him. What they saw shocked and horrified them.

(Cue Megalovania)

There were huge giant demonic wings coming out of his back, as long as huge demonic horns sticking out of his head. Instead of feet, he now had hooves. his vest was gone, allowing everyone to see the green marking on his body and face. He now only had his pants on him. His eyes were still glowing green.

Everyone didn't know how to act, they could't believe that this was Natsu. Some are hoping this was just a dream, while some are hoping this was just some sick trick he was playing.

"And now" Natsu became to speak again, but sounding much more demonic, "Gray, you're gonna burn in the twisting nether."

That was Natsu said before suddenly appearing in front of Gray, before slamming his fist into his head, sending him flying out of the guild into the streets of Magnolia. Gray was coughing up blood, as he struggle to get back on his feet. He noticed that it wasn't raining anymore, but the sky was now a dark and green color, with thunder happening all around, as if the entirety of Earthland was envelope in this dark and green sky.

Gray couldn't dwell on that right now, as Natsu suddenly appeared behind him. Gray made some distance between them before attacking.

"ICE MAKE LANCE!" he shouted as he unleash his attack on Natsu, but the ice melted before it even hit their attended target.

"Wha-?" Was all Gray got put before natsu unleashed a pillar of green flames from underneath him, hurting him and burning him in the process. He scream out in pain, until the pillar flame stop. He collapse one knee on the ground, trying to keep himself together.

"I'm not done with you yet dirty heart breaker." Natsu said before unleashing more of the green fire from his mouth, this time Gray manage to dodge it, but saw it heading toward the forest outside the town, and saw the attack completely wiped it out.

"HOW?!" Gray demanded, "WHAT KIND OF FIRE IS THAT?!"

"Heh, heh, heh," Natsu slightly laughed. "My fire is known as fel fire. It is fire of corruption and destruction unless you know how to control. And it is by these flames that you will know pain and agony like never before."

"NATSU!" multiple shouts have been heard from behind them. They looked to notice the rest of the guild heading toward them.

"NATSU, STOP THIS RIGHT NOW!" Master Makarov demanded. He didn't know that Natsu was capable of such power, but right now he needed to stop him from killing Gray.

"Why?"

"WHAT DO YOU MEAN 'WHY'?!" Erza yelled at him. "HE DOESN'T DESERVE THIS KIND OF PAIN YOUR GIVING HIM! I KNOW WHAT HE DID TO JUVIA WAS WRONG, BUT YOU REALLY THINK THAT THIS WILL FIX ANYTHING?!" Erza continued.

"Yes." Natsu blandly said. "This will put him in his place."

"Now where were we? oh right." Natsu continued while turning his attention back to Gray, ignoring the shock expressions of his guild mates. "Come on Gray, where's was that confidence from before?" He continued.

"If you want a fight flamebrain, THEN FINE, I'LL KEEP FIGHTING!" Gray shouted as he got ready to fight, ignoring the others protests. He knows he can't win, he knows that not even gramps could be able to stop Natsu, but if Natsu wanted a fight, he'll get a fight.

"Oh Gray," Natsu started to say with a grin on his face, "Your gonna have a bad time."