My Cute Wife is Mitsuri Kanroji

“I know you won’t die from this, so be prepared. This is revenge for Aunt Aiko!”

The demon looked at the tearful human who had just declared war against him. First that woman, and now this man... Why don’t they fear him?!

The demon couldn’t understand it. Even if he tried to think, the burning pain on his face distracted him. His cracked jaw and other injuries healed in a matter of seconds, and he jumped aside, out of Kotaro’s range. His physical injuries healed as if they were nothing, but the pain on his face persisted. The liquid that had splashed into his wounds caused excruciating pain.

A demon’s confidence lies in their belief in being unkillable. No matter the attack, no matter how powerful or skillful, a demon would recover from all of it. That’s why the demon was unafraid of an ordinary human. But his confidence shattered when Kotaro’s attack actually harmed him.

Though his wounds healed, the pain made it impossible for him to open his eyes completely, forcing him to rely on hazy sight and sound to fight.

‘Where is this pain coming from?’

Sniff~ Sniff~

He sniffed with his nose and detected a very familiar, hateful, and disgusting smell on his face. As a demon, it was a smell he knew all too well.

“Wisteria?”

“So, you figured it out. That’s right. It’s a poison made from wisteria.”

How can one kill demons?

First, slice off their head with a Nichirin katana. Second, fight until the sun rises. And third, use wisteria.

How could Kotaro, a reincarnator, not be prepared when he learned the world he lived in was the “Demon Slayer” world?

From the time he married Mitsuri, he started daily exercise to improve his fitness for both personal and combat reasons. But physical training takes time and doesn’t give instant results.

So, Kotaro took a path that provided instant results: poison.

Wisteria is deadly to demons; it can kill any demon if the amount is sufficient. Even a future Hashira, who lacked physical strength, adopted the use of poison to fight demons and later defeated an Upper Rank demon with it.

In case he ever encountered a demon, Kotaro kept a bottle of wisteria poison with him. And that bottle was what he threw onto the demon’s face.

“For now, it only causes pain and makes you blind, but as time passes, it will cause enough pain to make you unable to live.”

Though Kotaro confidently told the demon that its countdown had begun, he was actually very nervous. All his anger and adrenaline had gone into that one attack, and now he felt weak all over.

‘Why isn’t the demon dying?’

Even a small amount of wisteria is poisonous enough to kill a lower demon. This demon in front of him was the same, yet it wasn’t dead.

The demon’s face did have violet patches, a sign that the poison was working, but the demon was still standing despite it all.

‘Is it because it’s homemade?’

The poison Kotaro used was homemade. He wasn’t an expert in making poison, and he thought that it might not be potent enough.

But it was indeed working. At least, the demon couldn’t see at the moment. And as time passed, it would die from the pain.

‘I need to buy time for the poison to take full effect.’

If he could, Kotaro wanted to throw more of it, but unfortunately, that was the only bottle of poison he had.

His eyes shifted to Aunt Aiko, who was still breathing and alive. But considering the blood loss and her pale appearance...

‘No! There might still be a chance.’

A tear fell from his eye, but Kotaro still clung to the hope of a miracle.

…

‘It hurts! It burns!’

It was not an illusion. The pain, the damage… The demon named Ren could feel it. He could feel his body slowly giving in, and his death was not far off.

He just came out to eat some humans—why did he fall into such a state?

But what enraged him more was not the physical pain, but the mental anguish. Why… Why is the world not fair to him?

Why is he the one who was abandoned by his brother, while others weren’t?

Don’t all humans run in front of fear, abandoning everything? If so, then why don’t that woman and now this man?

Why…

Why did only his brother abandon him when he needed him the most, the time when both of them encountered a demon—the same demon he has become now?

The demon lost his sight, but he could still vividly see that day. The day when he and his big brother wandered at night, encountering a demon. And in fear, his big brother, who had promised to protect him from everything, pushed him towards the demon and ran.

That incident… Ren could see it as if it had happened yesterday.

It was his fate that the demon didn’t eat him and instead made him a demon. And from that day, he sought to witness it.

The miserable figure, the way humans abandoned others when they felt fear. And in his course as a demon, he met many, but now…

‘No! It can’t happen! I can’t be the only miserable one!’

“Aaaah!”

Ren shouted out, causing the cautious Kotaro to flinch. The demon clutched his head with his hands, as if he couldn’t accept it.

“I want it to be fair!”

Ren shouted as he blamed the world for making him the only one to feel it. He wanted to make others feel the same pain as him.

The pain of being betrayed by the one they trusted the most in the face of death. He wanted to see the same despair.

And for that…

Kotaro was agape. The pain that should have been burning him, rendering him immobile, yet despite the purple patches spread all over his body, the demon in front of his eyes stood straight, ready to fight him.

In anime, lower demons, all of them cry and beg for mercy when they face death. They pray for the slayers not to kill them.

But this demon… He isn’t even a ranked one, so why… Why does it feel like he has this aura?

Kotaro’s muscles tensed, and he too clenched his fist tight. He could feel the seriousness in the air. And the one who broke the tense moment was the demon. He pointed towards him and said seriously.

“Before I die, I will kill you.”

The demon was determined. But so was he. Kotaro took a normal boxing stance he had seen from the manga and replied, showing his determination.

“Don’t worry. The only one who will die is you, demon.”

===

A/N:

You’d probably tell me I'm milking the fight! But I’m not! I wanted to develop the demon’s character, giving him a reason for actively hunting humans rather than mindlessly killing and eating them.

Ren, the demon's name, was once a human who was abandoned by his only family—his big brother. He believed in and trusted his brother the most, but his brother ran away in fear, leaving him to face a ranked demon alone.

That betrayal shattered Ren’s trust and disillusioned him. He felt he shouldn’t be the only one suffering, so he sought to spread his pain to others.

That’s Ren’s backstory.

Also, I wanted to give some credit to Wisteria.

I’ve read a lot of "Demon Slayer" fanfiction, but I’m pretty sure none of the protagonists use poison to fight demons.

You get reincarnated, learn some techniques, and defeat demons. Isn’t that too typical and also a bit unrealistic?

Of course, it’s unrealistic unless there’s a system. Systems can be used to make anything unrealistic seem plausible.

But seriously, shouldn’t some reincarnators use poison to fight demons since it doesn’t require training and can pretty much one-shot normal demons? It’s like a gun that only needs one shot to kill a human.

Hmm... Now that I think about it, this could make a good fanfiction novel. Imagine a main character who doesn’t use breathing techniques but instead uses poison to fight demons.

That's all. If you'd like to support me, you know the drill—just head over to Patreon. Well then, see you tomorrow!