Reborn in black clover with Demon Slaying magic

Decapitation, a Demon Slayer's signature technique.

'H-He's dead...'

Having watched the entire fight from the distance, Nacht and his devils were at a loss for words. This was Lucifero, the king of devils. Someone who had lived for centuries. And he had died just like that? To a boy less than 20 years old? Just what was going on?

'After everything I've seen, to think that I was still underestimating him.'

Half manifested or not, Lucifero's power was real. Teamwork? Devil Union? None of it meant anything in the face of true power. But Grim, he surpassed all expectations and created a miracle.

'To make a devil feel despair, what a terror you are.'

Standing in front of Lucifero's headless corpse with one foot on it, Grim looked towards the sky and opened his mouth to let out an earth shaking roar. Filled with his feelings full of pain, victory and vindication, he made the ground tremble and shook the entire wasteland. 

Filling the hearts of everyone with a sense of pride and admiration, Grim's roar towards the heavens was one of conquest and defiance.

By the time the roaring ceased, his head suddenly snapped in the shaken Adramelech's direction.

!!!

With blood running down from his eyes, he looked truly demonic.

*Gulp*

A nightmare, that was the most accurate word to describe what Adramelech was seeing right now. Watching him take a step closer to him, his figure suddenly seemed to grow as the world around him dimmed.

'He's devouring light itself!'

-Crack!

Suddenly, numerous cracks started breaking out all over his skin once again.

'I'm running out of time.'

"Grim!" The Clover gang ran over to him.

Taking one last look at Adramelech, he shook his head and turned around to leave.

*Crack* *Crack*

Slower than before but still just as dangerous, the accumulated damage was begining to come back up in full force.

When he had told Lucifero that he might just die this time, he wasn't joking. But even so, he couldn't stop a smile from forming on his face.

This was the first time he had been injured so badly. And just by one person at that! Someone who wasn't even able to use their full power.

Looking down at his hand, he clenched it into a fist.

'This power, it isn't my limit!'

Smirking, he continued walking towards the area Lucifero had fought hard to reach. Ignoring the calls from his squad members, his heightened senses felt the disturbances in space.

This area, despite the castle having being reduced to dust, he finally understood where Lucifero was trying to go.

The ritual room.

Even if everything was gone, the mana here was highly unstable and the barrier that separated this this world from the underworld was incredibly weak.

'So that was your plan.'

To think that Lucifero plan was the same as his endgame.

*Grins*

Swiping his arm forward and activating [All Devouring], space tore itself apart and a rift in space and time formed.

With even more cracks breaking out on and even reaching his face. He looked incredibly fragile and it seemed like he was one the verge of breaking.

Looking at the worried faces of his "friends," he flashed them an innocent smile.

With a wave of his arm, he forced them all back.

Sensing that something wasn't right, Mimosa and the others had a flashback to the time he left them at the Heart Kingdom.

Shaking his head, Grim pointed at the cracks on his body and then at the wasteland.

'His body... It can no longer contain [All Devouring].'

"If he stays here, his power... It will consume everything." Nacht concluded surprising everyone.

"What!" Everyone turned to look at him.

'Him staying here means we'll all die?'

Refusing to believe it, Mereoleona rushed forward desperate to reach him.

-Boom

Casually waving his arm, the mana in front of her compressed and exploded outwards creating a force that pushed her back towards the others.

"What are you doing!" She yelled seeing more cracks appearing on his skin.

"Saving the world and finishing my job." He joked as the cracks on his skin started becoming more prominent.

'Thank god that Nacht guy came up with a convenient excuse for me.'

Honestly? He had no clue where Nacht had gotten the idea that he was losing control of his power and that it was on the verge of consuming everything. But at least this way, he wouldn't have to explain that he just wanted to go to the underworld to finish off Lucifero and the remaining Supreme Devils. Knowing these guys, they'd end up tagging along and annoying the hell out of him.

"WAIT!" Secre suddenly pushed herself to the front of the group.

"I'll seal those cracks and we'll find a way to-

"Secre." Grim smiled and looked at her with eyes that made her heart hurt.

"I-I can't lose anyone else." She said her voice trembling

"..."

"Why *sniff* Why do you have to go!" She cried. "Its not fair! Why do you keep sacrificing yourself and leaving me all alone!"

"I can't... I can't handle this again." She lowered her head tears welling up in her red eyes.

Seeing Lumiere's figure overlap with Grim's, she couldn't stop the tears from flowing down her face.

"Please, please don't leave me alone again."

"Secre..."

As cold heart and ruthless as Grim was, knowing about the trauma this girl suffered through for 500 years and guessing that she had some unresolved abandonment issues, he couldn't help but hesitate for a moment before steeling his resolve.

For the sake of his goal, he couldn't afford to let feelings get in the way. It hadn't stopped him before and it wouldn't start now.

"Secre." He spoke up again but this time with more confidence in his voice. "You don't have to worry about me. After I sort this out *points at cracks* I'll be back before you know it."

"*Sniff* Grim..."

"C'mon, don't cry." He smiled. "I promise this won't be the last time you see me (because I still need someone to help raise my kids), don't think of this as goodbye. Just think of it as me going on a long vacation (a genocidal one), in fact, while you wait for me, you might as well spend some time at the new Elven village (and learn some child rearing skills). The descendants of Licht still need you (get them ready for war with my kids.)"

*Sniff*

She wiped away her tears. "You promise this won't be the last time I see you?"

"Yeah, I promise."

Having finished reasurring Secre, he gave the others some comforting words before staring into the rift.

"Hey Grim!" Mereoleona suddenly called out. "When you come back, I'm gonna be super strong and I'll kick your ass! So hurry up and come back soon you hear!"

"Heh." He smiled. "I look forward to it."

Stepping into the rift, he suddenly vanished before everyones eyes.

Meanwhile...

*Flap* *Flap* *Flap*

'What the hell! I really thought I was about to die!'

Flying through the air and clutching Lucifero's bleeding heart, sweat covered Adramalech's forehead.

Thankfully, those humans were too busy saying their goodbyes to realize that he had ripped out Lucifero's heart and made off with it. With this, he had already completed his role.

As for those first layer devils that weren't fused into Lucifero's worm form, he was confident that he could rally them up and make them submit with his rank as a Supreme Devil. But before all of that, he had to reach the Clover Kingdom and give the heart to the one who had set all of this in motion.