Doomguy X Demon Slayer

The Last Battle

Doomguy, with Crucible firm in hand and BFG-9000 on the other, stood his ground as Kokushibo charged. A loud clash shook every corridor, every room, and every corner. The last battle had begun. Doomguy received very little but shockingly fatal blows. His armor was damaged, he sustained massive slashes and he was struck with bruises all over! But he did not care. Kokushibo was willing to win the fight and prove his unwavering loyalty to his master, while Doomguy wanted to finish the job and get the hell outta there. In the middle of the battle, it was finally Doomguy's turn to do some damage. He left gashes, slashes, stabs, cuts and other classifications of bleeding injuries on Kokushibo, but was unable to sever any limbs.

Doomguy saw that Kokushibo had fragile pride, so he decided to make Kokushibo feel weak by pretending he felt ABSOLUTELY NOTHING. He stood still like a statue while Kokushibo tried so hard to leave so much as another scratch on him. Kokushibo, angered, decided to raise his sword and try to cut off Doomguy's arm. When the blow landed, his sword broke, and Doomguy let out a little chuckle. A slight giggle. A tiny guffaw. A miniscule snicker. A bite-sized laugh. Kokushibo stood there in shock, with his sword on the floor. Immediately, he felt something as hot as the sun and as sharp as a Japanese oriented kitchen knife stab him in the back. He looked behind him, and saw Doomguy who had landed an excruciating attack. Doomguy pulled the sword back and simply waited..

Kokushibo, confused and angered as to why he couldn't do so much as dent Doomguy's armor anymore, became enraged. With his pride now at a breaking point, he started attacking at rapid speeds! Doomguy, now quite pissed, began to track Kokushibo's every move and soon enough, he was able to grab his wrist. Kokushibo had stopped completely, and was slammed on the ground and ceiling. Kokushibo, while in the air, used his broken sword to knock Doomguy's helmet off, revealing his smirking face. Doomguy continued to not care and threw Kokushibo across the room, resulting in a plethora of his bones to be broken. Kokushibo regenerated and continued to try and harm Doomguy in the worst ways. Doomguy was not affected in any way and punched Kokushibo in the chest, sending him flying to the other side of the room.

Kokushibo, now weakened, knew what he had to do now. He decided to take on a more beastly form and ran right towards Doomguy. Doomguy used his Crucible to lop both arms off, causing Kokushibo to yell in pain and fear. Kokushibo started using his monstrous fangs to bite and lunge towards Doomguy. Multiple injuries were inflicted on him and Doomguy returned to his senses of marshal prowess. He singed through the flesh of Kokushibo and eventually blasted his head off with a fully-charged shot of the BFG-9000, leaving pools of blood on the floor. Doomguy grabbed the head and threw it out the room, and eventually out of the Infinity Castle, where it would fall somewhere really far away, but not disintegrate.

Meanwhile in the other rooms, the fellow slayers were mortally injured. They were closer to death than decisive victory and didn't know what to do.... until all the demons they fought suddenly died. A door appeared in each room and they were free to find Muzan again. Only this time, they were farther away than they were closer.... They started running to their desired location and eventually met up in one area with Doomguy, both holding his helmet and covered in blood. Doomguy put his helmet back on, and led the way. They soon found Muzan and the final encounter began.

Muzan took his final form and started throwing attacks at the slayers. He was too fast to dodge or out-maneuver and Doomguy stepped in when times became VERY desperate for the slayers. Muzan had become even more monstrous than before and started landing decisive blows on each and every slayer present in the Castle. Doomguy fired the BFG-9000 to try and decapitate the tentacles protruding from Muzan's back. As the tentacles fell to the floor, Muzan roared in anger. He directed all attacks on the Doom Slayer and inflicted massive damage. Doomguy used the meathook of his Super Shotgun to pull himself to him, allowing him to shoot Muzan in the face. Muzan, blinded, did not know what to do. While distracted, Doomguy fired the BFG-9000 one last time, and blew Muzan's head off. As Muzan cried out in shock, a giant cosmic eye opened in the midst of the battle and looked at Muzan's head. Muzan yelled "DO IT!" as his head disintegrated, triggering the cosmic eye to look at Tanjiro and squint, unleashing a deadly, power of transformation. The cosmic eye disappeared before Doomguy could do anything, and Tanjiro curled up and fell on the floor. As other slayers were mourning the losses they faced, they soon ran to him in shock, fearing for his death. Fellow slayer Genya had been severed in two, while fellow Pillar Tengen had been stabbed in the eye and through the brain. At this point, they could not bear the loss of yet another slayer... or so they thought. Tanjiro got up and stood in a crouching-like position, looking at his friends one last time. His friends immediately stepped back as they made a horrifying discovery... Tanjiro had become the new Demon King.

Doomguy immediately ran to try and subdue Tanjiro so he could hopefully revert this strange curse and mend the timeline but Tanjiro jumped away... A voice then spoke in Doomguy's head, drowning out all the crying and confusion.

"Let him run. This is a part of the timeline. There is no need to interfere anymore... Oh, and about the sudden deaths.. you can leave them be." 

Doomguy then looked at the demon slayers one last time and exclaimed...

"I have to go."

A portal opened behind him, and he began to walk to the gateway. But then someone yelled out;

"YOU'RE JUST GOING TO LEAVE US LIKE THIS? AFTER ALL THAT'S HAPPENED?"

It was none other than Inosuke, in tears because Tanjiro had become a demon and because 2 of his friends perished.

"My task is done. There is nothing more I can do." Doomguy sighed as he entered the portal and vanished...

"DAMN YOU!! YOU'D BETTER START PRAYING IF I EVER SEE YOU AGAIN!!!!" Inosuke yelled as he punched the floor with tears streaming down his face...

But Doomguy was no longer there. He had already returned to rest in his tomb, preparing for the next events.....

THE END.