If immortality was the ultimate goal of any demon, their reason for being and their greatest dependency...
Then Blood Demon Art was their calling card. What made them unique.
And sure, maybe Marcus couldn't get his hands on the best cards in the deck. But the small cards have their uses too. Played right, combined well... they can build something monstrously powerful.
Besides, there was something else.
A hypothesis. Small. But if it turned out to be true... it would be huge.
Muzan... did he count as part of the Twelve Kizuki or not?
Because if he didn't count... did that mean he could devour his Demon Art?
If he could exploit that loophole, in the future he...
'Tsk...'
Just imagining it gave him a certain satisfaction. Muzan, who had spent his entire existence devouring people... ending up being devoured by someone else. That would be delicious.
Though of course, that was nothing more than an assumption.
He didn't know if it was possible. And even if it were, it's not like he could just go and do it. Before dreaming about devouring Muzan, he first needed to think about what kind of Blood Demon Art to devour that would allow him to kill him.
And not just any way. He needed a method that wouldn't let the sunlight get to him too early, because if Muzan turned to ash... goodbye feast.
To pull that off, the reward from human women became the top priority.
Without the Transparent World, he wouldn't be able to locate Muzan's vital points or slice him open following the exact lines.
Without the Red Nichirin, even if he managed to hit those vital points, it would be useless. Muzan would regenerate in a matter of minutes.
And the last resort... the Demon Slayer Mark.
Speaking bluntly, that was basically forcing a lethal dose of adrenaline into the body. A brutal surge of power with a very clear price: once activated, you wouldn't live past twenty five.
And that was precisely what Marcus didn't want.
Because he was almost certain the system would give him an activated Mark, not an innate one. And he had no intention of dying young just to kill an androgynous freak.
But unfortunately, the trio of rewards was random.
And according to Murphy's Law, unless he decided he didn't want any of the three pieces and spent the rest of his life simply being a "demon"... the most likely thing was that the first one he'd get would be the Mark.
Because that's how luck works. Always against you.
And even if by some cosmic miracle his luck turned out to be absurdly good and in two attempts the Mark didn't come up... that still wouldn't save him.
Before the great decisive battle at the Infinity Castle, someone would activate it, and from that point on... the Mark would spread like a plague. And he... damn it, as long as he wasn't hiding under a rock, sooner or later he'd be infected.
'...but thinking about it...'
He needed a Plan B.
Activate the Mark and not die. Up until now, in all of history, from what he knew, only two beings had managed it.
The first was Yoriichi, but he didn't count. That monster had been born with the Mark. He was a walking exception.
The second... only one had truly pulled it off.
Yoriichi's brother. Michikatsu.
Or rather... Kokushibo.
And the path he took to survive after activating the Mark was...
Exactly.
Marcus's Plan B was to become a demon.
But hold on. Not just any demon. Not one of those deformed things that died in sunlight, that had to devour people to exist, that lost their memories, with twisted minds, living with a noose around their necks because Muzan could kill them whenever he felt like it.
None of that.
What Marcus wanted was something more like Tamayo, someone who on the outside was indistinguishable from a normal person. Free from Muzan's control. No need to eat humans, just a little blood and done.
More than a demon, he preferred to call her... a vampire.
And Marcus was willing to do whatever it took to become that creature.
With one condition, of course: solving the small detail of "sun = death"
And the key to solving that problem... was sleeping right in front of him.
From what he remembered, there were many theories about why Nezuko didn't fear the sun after becoming a demon.
The most popular was the Blue Spider Lily theory.
The theory said that the Kamado family had had that flower nearby for generations. Basically, the flower Muzan had been desperately searching for over four hundred years... the Kamados had been eating it like it was just some wild vegetable. And thanks to that, Nezuko had developed the ability to coexist with the sun.
It was a good theory. Too bad it was debunked.
The Blue Spider Lily only bloomed two or three days a year. Each bloom lasted barely ten minutes. And it always happened during the day, which explained why Muzan never found it.
On top of that, it was explicitly mentioned that Tanjiro had only seen it once in his life, by pure chance, when he accompanied his mother to visit a grave.
So whether Nezuko's immunity to the sun was related to that flower or not... remained an unsolved mystery.
Then there was the genetic theory. The Kamados had passed down Sun Breathing disguised as Hinokami Kagura for generations. Maybe that legacy had altered something in their blood, in their genes, and that's why both Nezuko and Tanjiro, upon becoming demons, retained the ability to walk in the light.
And lastly, the most romantic theory of all: that Nezuko had never drunk human blood. All her power came from protection. Even to recover, she relied solely on sleep. Perhaps... the sunlight simply found no reason to destroy her.
Whatever the correct answer was, Marcus was no longer sure of any of them, and what he did know for certain was that he wasn't going to take the risk.
Feeding Nezuko his blood would benefit him.
But there was also that tiny possibility that by tasting blood, Nezuko would lose forever the chance to develop sun immunity.
And that was not a risk he could afford.
Tie Nezuko to his side two years ahead of schedule? Tempting. But after thinking it through, he felt the right thing to do was to let Nezuko follow her course.
Let her develop according to her destiny.
At least the general direction couldn't change.
And if everything went well, she would become the key. The exact piece Marcus needed to obtain, in the future, the perfect lineage of a vampire.
But before reaching his ideal... strength came first.
Squishing Nezuko's adorable little face, he said to the system:
'Give me the beginner rewards.'
Instantly, an avalanche of memories that weren't his flooded his mind all at once, and at the same time, a long jet black sword materialized in his hand.
The basic sword technique was settling into his head with every passing second, becoming sharper, clearer, more his own. And without thinking, with a deftness he hadn't had five seconds ago, he unsheathed the Nichirin the system had granted him.
He executed a series of cuts. Fast. Precise. Elegant.
Nothing changed around him. Not a breeze. Not a sound.
Only three hairs appeared on the blade. Perfectly cut. Perfectly aligned. Evenly distributed.
Marcus smiled.
The technique was basic. It was simply the purest and most fundamental control over a sword. But that control allowed him to handle it as if it were his own finger.
And that, for a start, was more than enough.
As for the sword itself...
It wasn't a katana.
At first glance they might look similar, but someone who knew about swords would notice the differences instantly. The edge and blade of a katana have curvature, designed for slashing cuts, not for thrusting. But the one Marcus was holding was different: straight, no curvature.
Now, to be fair, at the current stage and for the purpose of killing demons, a katana with its wide, flat edge was technically more suitable. That design was optimized for decapitation, which at the end of the day was the most direct way to eliminate a demon.
But the katana also had a fatal flaw.
To maximize its lethality, its edge was ground very deep, which left the spine of the blade dangerously thin. Result: sharp like few others, but fragile. Easy to bend, easy to break, easy to chip.
That explained something that had always caught his attention about the series. Against fragile enemies, the slayers could decapitate with a single clean slash. But the moment they ran into some high defense demon... one hit, and they were already fighting with half a sword.
Though well, whether it broke or not wasn't really the important thing here.
The system had already made it clear: custom forged weapon, special, unbreakable, indestructible, zero wear. Ever.
What Marcus liked most, being honest, was something else entirely.
Its appearance.
'It was awesome.'
Gripping the handle with one hand and holding it upright in front of his chest, he inhaled deeply, closing his eyes for a moment.
'Breath of Desire!'
!
A faint pink glow began to climb from the base of the blade and merged with the white steel until the entire surface took on a purplish pink tone.
Marcus narrowed his eyes, gazing at it.
'I love it...'
But that wasn't all.
As the first reward from the system, as the companion that would stay with him for the rest of his life... this sword couldn't be something simple. And it wasn't.
According to the system, it had been custom forged, based specifically on the Breathing Technique the host had awakened. That meant it came with a special ability. Or more than an ability, a distinctive trait.
Something unique.
Something that only that sword and that breathing could produce together.
If he had awakened Water Breathing, perhaps the sword would be extremely flexible. Thousands of variations in every movement.
If it were Fire Breathing, maybe each cut would carry a burning abrasion. An edge that scorches. Almost a half baked Red Nichirin.
Thunder Breathing? Paralysis and electric discharge with every cut.
Insect Breathing? Built in poison.
The combinations could be infinite, and he had no way of knowing what they all were.
But what he could confirm, what the system revealed to him about the trait corresponding to his Breath of Desire, was...
It nourishes the soul!
________
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