Explosions could be heard all over the forest, as a young boy and a madman could be seen fighting until one of them dropped dead. Subaru charged at Petelgeuse, dodging any Unseen Hands that came his way and swung the Demon Slayer Sword at the Archbishop. 

Petelgeuse was able to block the attack with his Unseen Hands as Subaru got swatted away by a hand and got sent flying. Subaru was able to recover and dodged more of the Unseen Hands. Though Subaru was reaching his limit, he didn't know how long he could hold out. There were so many hands, that he couldn't dodge and attack them all at the same time.

"Damn! If this keeps up, I won't be able to hold out much longer!"

Subaru focused and tried to use his Ki-sensing to try and sense Sloth's movements, as he dodged a hand but couldn't react in time, as an Unseen Hand grabbed Subaru by the leg and began to lift him up into the air. With quick thinking Subaru summoned the Demon Dweller Sword and and cut the hand before it could even slam him to the ground.

Subaru quickly and swiftly dodged all the hands and threw The Demon Slayer Sword at Petelgeuse as he dodged it. But when he turned around Subaru was nowhere to be seen. 

"Up here you bastard!"

The madman looked above him only to see Subaru swing both his Anti Magic Swords down on him. The impact was so much that Subaru formed a crater under him creating a dust cloud. Subaru quickly got of the Archbishop as more Unseen Hands shot towards him.

"SATELLA! SATELLA! GIVE HER TO ME!!!!!!"

"Damn! You don't know when to give up huh!? What about you is so slothful now? Your working pretty damn hard to me!"

Subaru dissipated his swords and summoned his Anti Magic energy, coating it around his arms as he charged at Petelgeuse letting out a battle cry as he did. It was now close quarters combat,  As Subaru was dodging any hands that came his way and threw a punch towards the madman's face, sending him flying meters away. Not without Petelgeuse sending Unseen Hands punching Subaru all over his body.

When Subaru  turned around and began to head for the mansion, he heard the madman scream as he turned around and saw two huge Unseen hands charging right towards him. Subaru had no time to react as the Unseen Hands grabbed him and slammed him into a bunch of tree's and threw him meter's away from the mansion. With Subaru out of the way, Petelgeuse charged straight for the mansion with only one objective in mind.

Subaru was crashing through trees until he came to a stop. Subaru felt unbearable amounts of pain as he couldn't even move. Images flashed through his mind as he remembered all the times he spent with the residents of the mansion, Subaru could feel himself succumb to unconsciousness as he was trying his absolute hardest to get his body to move but he had not luck. When Subaru passed out, dark fog seemed to take over as a certain Witch appeared and said one sentence.

"Love you."

 When Subaru came to, he was just floating around in a dark room of nothingness until he heard a voice behind him.

"YO!"

"WELCOME!"

When Subaru turned around, what he saw shook him to his very core. It was some big black humanoid creature with big clawed hands and black wings just staring at him.

Subaru could only stare in utter shock and fear at the creature until it spoke again.

"NOW THIS IS SOMETHING, I NEVER SEEN NOR HEARD OF A DEVIL SUCH AS YOURSELF HAVING A DEVIL INSIDE OF HIM. GUESS THAT MAKES YOU THE FIRST DEVIL TO BE A DEVIL HOST." 

"EITHER WAY THIS IS A PERFECT CHANCE FOR ME TO APPEAR IN THE PHYSICAL WORLD. SO I'LL BE TAKING YOUR BODY."

As it tried to grab Subaru, he quickly moved out of the way not trusting this guy, not one bit.

"Why in the hell would I let you take my body?"

"COME ON IT'S NOT A BAD DEAL. YOU WANNA WIN DON'T YA? AGAINST THAT HUMAN?"

"I want to beat that guy with my own strength, on my own terms!"

The Devil grabbed Subaru as it said...

"JUST SHUT UP AND LET ME TAKE OVER YOUR CONCIOUSNESS ALL READY. ALL YOU HAVE TO DO IS PASS OUT. AND I'LL TAKE CARE OF THE REST. THERE ARE SOME PLACES YOU JUST CAN'T CLIMB. GIVE UP."

Subaru was just about to do that until he remembered Rem's words.

"Giving up is easy. But it doesn't suit you."

"Even when on one else will believe in you...I'll still believe in you!"

So let's start from square one...no from zero!"

"Show me how awesome you can be Subaru-kun..."

"Sorry but I can't do that...because I have someone who believes me!"

The Devil slammed his hand on Subaru to make sure he wouldn't get back up.

"YOU MAY HAVE LEARNED HOW TO USE YOUR ANTI MAGIC BUT YOU STILL CAN'T USE IT TO IT'S FULL POTENTIAL YET. LIKE I SAID GIVE UP."

"Give...up...?"

Right then and there, flashbacks of all of Subaru's previous loops replayed in his mind. As he remembered Crusch refusing to help. Anastasia setting him up for personal gain. Priscilla man handling him and threatening to destroy the Emilia Camp. Puck killing him and calling him useless. Emilia leaving him in the capital. Julius beating the crap out of him as he told him he wasn't fit to be by Emilia's side. Emilia leaving him in the Capital. And Rem dying in his arms as he screamed in rage. 

As these memories crossed his mind, he could feel his Anti Magic energy coating around his arm as well as the Devil's power entering him as well. Black marks went passed his arm and went across his chest area and towards his cheek. And the left side of his hair was completely pitch black, darker than his right side. 

"On that day I promised myself that I would protect them...and I intend to keep it!"

Subaru felt all of his power and the Devil's power completely enter him as he let out a rage filled scream. When Subaru regained his consciousness, he opened his eyes wide while black energy swirled around him and completely covered him. When the black energy dissipated, he now had a huge black wing on his right side along with his right arm being completely black, with black markings on his chest area and cheek. His right eye was red while his left eye stayed the same, the right side of his hair became pitch black as he grew a black horn, as his tail also became pitch black and grew longer. While his left side stayed the same.

Subaru summoned the Demon Slayer Sword as it also became pitch black. Subaru looked up at the sky and screamed at the top of his lungs.   

"..."

Julius went through the mansion's doors and immediately went to search for Emilia and everyone else. As he roamed the hallways he began opening doors for what felt like an eternity.  until he opened a door...only to find a library with Emilia, Rem, Ram, Otto, The Iron Fang, and all the villagers all in one place. And a very irritated Beatrice.

"Emilia-sama! Are you alright!?"

"Yes. I'm fine Julius...But where's Subaru...Wasn't he with you?"

"...Natsuki Subaru is fighting Sloth right now as we speak.

Right as he said that, they all heard an explosion nearby. Emilia, Rem, Ram, Julius, Ricardo, Felix, Otto, The Villagers, and the rest of the Iron Fang went out to go see what caused it while Beatrice, having heard the commotion stayed inside, watching from a nearby window. And what they all saw made their blood run cold, it was a crazed highly injured Petelgeuse charging for them. 

"Witch Cultist!"

As soon as Petelgeuse locked eyes with Emilia, he began to cry happily seeing her.

"Ahhhh! Ohhhhh! My love! The purpose of my diligence is here! Oh! Oh! Yes! So wonderful!"

"Lia! Get back!"

Petelgeuse sent his Unseen Hands at her until right then and there, a black line came crashing down right in front of Emilia. Wiping out the hands completely.

Emilia stared.

Rem stared.

Ram stared.

Puck and Beatrice stared.

Everyone stared. The disbelief they had in seeing Subaru fighting someone was feverish.

"S-Subaru...?"

"S-Subaru-kun..."

Emilia and Rem could only say his name as they were looking at him. Covered in wounds all over his body, his tracksuit jacket was halfway destroyed, and his appearance...was just demonic. Rem and Ram noticed that he had a horn, completely shocking them. Ram held her hands to her chest as she uttered.

"I-Impossible. Barusu?"

"Curse you! Curse you! Why do you keep getting in the way of my love!? Whywhywhywhywhywhywhywhy!? Tell Me!!!!''

Petelguese ranted as he sent Unseen Hands towards Subaru. Subaru swung his sword completely wiping them out as he charged roght towards Petelgeuse in a blink of an eye and launched him in to the sky. Subaru them followed flying into the air while Petelgeuse used his Unseen Hands to keep him from falling. Everyone just stood there shell shocked, Subaru was flying like it was nothing seemingly dodging something they couldn't see.

Petelgeuse launched more Unseen hands towards Subaru as he dodged them at incredible speeds. Subaru flew back in, charging at Petelgeuse. Petelgeuse grabbed Subaru by the head and began squeezing it, thinking he won until Subaru grabbed his arm and threw him towards the ground making a crater underneath as Petelgeuse cough blood.

As Subaru flew back down in front of everyone, Petelgeuse could only look in fear as he realized at that moment that Subaru was no human. Petelgeuse shook in fear and anger as he used his Unseen Hands to retreat.

"G-Get away! GET AWAY!"

Petelgeuse roared as he used his Unseen Hands to carry him away through the forest. Though Subaru wasn't going to let him get away, he closed his eyes and focused, tracking his Ki.

https://youtu.be/PLV23C5VPgI

And in a blink of eye Subaru was right behind Petelgeuse, chasing him through the forest. Petelgesue turned around and launched Earth walls and Earth spikes towards Subaru, creating a huge smoke screen. Subaru kept on dodging the spikes and blocking them. Petelgeuse kept shooting more at Subaru, pushing him back far enough, making a huge explosion. Soon after Petelgeuse made a huge wave of rock and launched it towards Subaru. The wave so huge that it covered the whole forest killing anything in it's path. 

Everyone that was watching the fight could only watch with baited breaths. As Emilia screamed out his name in worry, thinking that he to was hit. Until she saw a black line flying through it like it was nothing. Subaru was flying towards Petelgeuse, negating any magic he threw at him and with one swing of the sword the earth magic was gone. Subaru quickly charged at Petelgeuse swinging at the Unseen Hands and his earth magic. Petelgeuse combined all of his Unseen Hands into one giant Unseen Hand and shot it towards Subaru. Subaru flew through the giant hand and punched Petelgeuse square in the face making him fall over. 

Petelgeuse soon used the hand to grab Subaru and threw him with full force towards the forest. He than used everything he had to take Subaru down and sent numerous earth clubs and Unseen Hands towards Subaru, pushing him back towards everyone watching the fight. Subaru began walking towards the Archbishop shadow covering most of his face but you could see a red glow as he was walking towards Petelgeuse growling as he did.   

Beatrice continued to watch...with some panic across her lovely face. 

"I sense no mana being used whatsoever. No mana influence, yet he erasing all the mana in the air like it's nothing. That isn't magic he was using...what is it? What is this? What happened to this boy?"

Petelgeuse was still in the air breathing heavily shacking with anger at the boy in front of him, no matter what he did it wasn't enough to take this boy down.

"Why? WHY DO YOU RESIST ME SO MUCH!? I HAVE BEEN NOTHING BUT DILIGENT!!!! DILIGENT!!!!!! FOR THE WITCH!"

Petelgeuse bit off his finger nails to summon more hands and launched them at Subaru. Subaru just kept walking and breathed, quickly charging forward leaving nothing but a black line. Subaru chased Petelgeuse as they both flew in the air, the Archbishop was doing everything he could to get away from Subaru but nothing worked.

"What are you? JUST WHAT ARE YOU!?"

"I'm Natsuki Subaru! The knight of the Half Elf Emilia...and I'm also A DEVIL!!!!"

As Subaru said this Petelgeuse could see something that made him feel fear for the first time in decades, Petelgeuse saw a black demonic figure right behind Subaru as he charged forward.

"This is it Petelgeuse! This is where you lose! Your finished!"

Subaru pulled his sword back and sliced through the Archbishop leaving a black line as he did.

"Black Strike!"

Petelgeuse began falling, while Subaru flew around and landed right in front of everyone that was watching the duel while Petelgeuse could only scream his name in rage while he was falling.

"CURSE YOU! CURSE YOU! NATSUKI SUBARU!!!!!!"

Petelgeuse landed on the ground as he only shook in pain.

"I-Impossible...impossible...this shouldn't be happening."

While Petelgeuse was dying, the fatigue caught up to Subaru as his Anti Magic energy dissipated along with his swords as the black markings, and his horn dissapered. His tail went back to it's normal size as he passed out and fell over. Emilia, Rem, and everyone else that was close to the boy instantly ran up to him making sure he was ok. 

"Subaru!"

"Subaru-kun!"

Rem and Emilia instantly got to work healing him meanwhile Petelgeuse with the little strength he had sent Unseen Hands towards Subaru, he wasn't going down without taking the boy with him. No one could react in time as they noticed to late. Until a portal opened up and out of it came a young man wearing a black scarf and a black jacket. The mysterious individual quickly destroyed the hands as Petelgeuse took his last breath and died.

Petelgeuse was finally defeated. For good.