Muzan's Heir | Demon Slayer: Kimetsu no Yaiba Fanfiction [Mitsuri Kanroji, OC]

The Successor of Kibutsuji Muzan

If one were to witness the gruesome battle between Muzan and Tokimune, they would witness war between monsters. "You... I won't let you take my son's life like you did my wife's!"

"What are you babbling on about?" Muzan asked in bewilderment to the greatly injured swordsman — but instead of answering back, Tokimune leaped forward with his blade to fulfill a downward slash to the demon.

Sadly, this demon was too quick on his feet and evaded the strike, stepping one foot to the right and making his adversary miss completely. "Tell me, what did you mean by your previous statement?"

Muzan jumped back greatly to give one other breathing room. "Well? I'm waiting..."

"You killed my wife! Don't you dare act clueless, you damn demon." The former flame breather struggled to get out those words as his lungs collapse and his knees buckled due to tiredness.

Damn my old age. Tokimune mentally cursed.

And as our protagonist's father struggled to lift himself from the ground, he could've sworn he heard Muzan laughing — and laughing, the demon king was. "Oh, I see your misunderstanding."

Misunderstanding? Tokimune asked himself. He wondered cluelessly what his opponent might've meant, but it wasn't long before he was served with answers.

"As much as I would've loved to slit that wretched sun breather's throat myself, one of my loyal followers beat me to it... unfortunately."

There was a strict pause in conversation as Tokimune's great revelation started kicking in — Muzan wasn't Amaterasu's cold-blooded killer. But if that's the case, then who is?

"Then, tell me that demon's name!"

"Why? Do you wish to seek him out? In that condition?" Muzan questioned. "My, do I admire such willful being. It's almost upsetting that you have to die."

And the fight rages on with the fossil-looking old man turning into a giant, muscular young lady — Muzan started altering his physical appearance. The most notable changes were his newly formed build, his height, and face.

"Shall we resume our quarrel?" He — or rather she — was terrifyingly huge, almost as big as the snowy trees surrounding her, yet Tokimune held his family's heirloom with unwavering courage and waited for his adversary to come charging at him.

***

"Worthless." Akira heard. "After all the trouble I've gone through is only when I realized that you weren't even a sun breather... how disappointing."

After an hour long sleep, the red-haired boy started to finally come to his senses for good. His sight was still blurry, but the figure in front of him was clearly of a woman's.

"But, undoubtedly being the descendant of a sun breather is sure to give you vital strengths. How could it not?" The woman continued monologging.

"Who are you?" Akira croaked before finally feeling his hurting body — his lungs were sent aflame, ribs broken, and insides bleeding.

He coughed out heaps of blood and upon looking to his left, he saw the clear beheaded corpse of his father laying lifeless on the red snow. He gazed further, lifting his head off the ground more to see, but he wished he didn't.

Now, all he yearns for is to be dreaming and shall soon be woken up from his nightmare by his still living father. Sadly, it wasn't destined and reality is as cruel to him as it is to anyone.

The mysterious, giant woman towered over our protagonist and sighed visibly. "It must be hard for you to see someone so dear become only laid waste."

She approached the still disturbed boy and with her huge finger, she placed it pointing on Akira's forehead. "Rest easy, son of Hojo, you will reunite with your loving parents soon enough."

Akira's eyes grew wide as he was suddenly impaled — his skin turned ash grey and his whole body started spazzing out due to gallons of Muzan's own demon blood mixing with his own — this is the end for me, there's nothing more I could do is what he would've thought if his mind didn't become numb.

Akira helplessly look onwards at the smiling woman killing him. "Bye-bye, Inheritor of the sun bre—"

But, before anything more could happen to the young man, another strong whirlwind-like force joined in on their affairs. Only, this one never minded Akira and went straight for Muzan — she quickly jolted her head back to avoid it's fierce attack, yet it cut off her arm completely as a repercussion.

The demon king hopped far enough away from the looming sense of danger, but a deep cut still manage to appear on her left cheek and an irritated face was displayed clearly for anyone to see — she was not amused. So, with a swift and smooth transition, she reformed herself once more.

Now, the previously colossal woman is but an averagely tall man with pale skin; he has long, jet black, and curly hair. But, the most prominent feature — and the one that stuck out most — were his eyes, for they're glowing fire engine red. And of course, all injuries initially dealt to his body were now healed completely.

"Show yourselves!" He demanded, yet no one step up which agitated him thus more.

Suddenly, there was a sharp ringing noise protruding in Muzan's ear that raised hairs on the back of his own neck. He looked all around him, but failed to find it's source; and as the sound's frequency continually climbed higher, it had reached the point to where the demon's lugs bled.

"STOP!" Muzan yelled out loudly in pain. "Stop this at once — argh!"