If immortality is a demon's bottom line and greatest reliance,
Then Blood Demon Art is a demon's upper limit and greatest display of prestige.
Even if Shirakawa doesn't get the best cards, even the smallest cards have their own ways of being played.
If used well, they can still form an overwhelmingly powerful existence.
Furthermore...
In Shirakawa's heart, there was a faint idea—small, yet grand.
Does Muzan… actually count as one of the Twelve Kizuki?
If he doesn't, could I devour his Blood Demon Art!?
If this loophole can be exploited, then in the future…
Tsk…
Muzan has spent his entire life devouring humans. If he were to be devoured by someone else in the end… just thinking about it is satisfying.
Of course, this is only speculation.
Whether it can actually be achieved is still unknown.
Even if it is possible, it's not something he dares to consider right now.
Rather than thinking about devouring Muzan, he should first consider what kind of Blood Demon Art he could obtain to kill him.
And it must be a method that prevents sunlight from touching him—otherwise, Muzan would turn to ash and become impossible to devour.
To achieve this goal, the human-side rewards—the trio of combat abilities—become the top priority.
Without the Transparent World, he wouldn't be able to strike Muzan's vital points or cut along the precise lines.
Without a Crimson Blade, even striking Muzan's vitals would be meaningless—he could regenerate within minutes.
As for the Slayer Mark…
To put it bluntly, it's nothing more than forcibly triggering a lethal dose of adrenaline.
Once activated, one wouldn't live past the age of twenty-five.
This was something Shirakawa absolutely did not want.
After all, the system clearly stated it was an "activated" Slayer Mark, not a "natural" one.
He had no intention of dying young at twenty-five just to kill someone like Muzan.
What's the point? Why should he?
Unfortunately, the three rewards are random.
According to Murphy's Law, unless he gives up everything and lives his life as a "Demon Knight,"
The first ability he unlocks will most likely be the Slayer Mark.
Even if his luck is extraordinary and he avoids unlocking it twice,
Before the final battle at the Infinity Castle, someone will inevitably awaken it.
And as long as he doesn't isolate himself, he will eventually be affected by it.
…Tsk, the more he thought about it…
The more Shirakawa felt he needed a backup plan.
To activate the Slayer Mark and still survive… currently, aside from the naturally marked Tsugikuni Yoriichi,
Only one person had achieved it—
Tsugikuni Yoriichi's older brother, Tsugikuni Michikatsu!
Or rather, the current Upper Rank One of the Twelve Kizuki…
Kokushibo!
Looking at the path he took to survive after activating the Slayer Mark—
Exactly!
Shirakawa's backup plan was…
To become a demon!
Of course, not the kind of grotesque demon that burns in sunlight, must consume humans, loses its memories, becomes mentally twisted, and can be erased at any moment by Muzan's control.
What he wanted was something like Miss Tamayo—
A being no different from a normal human in appearance, free from Muzan's control, and only needing to consume blood to survive.
A demon like Miss Tamayo… rather than calling it a demon, Shirakawa preferred to call it—
A Vampire!
If Shirakawa felt resistance toward becoming a demon, then toward becoming a Vampire, he felt the complete opposite.
He would gladly embrace such a being—one standing at the top of the food chain—with absolute enthusiasm.
Of course, the prerequisite was solving the problem of "sunlight = death."
And the key to that problem lay in the sleeping little girl before him—
Nezuko!
In his previous life, there were many theories about why Nezuko did not fear sunlight after becoming a demon.
The most widely spread theory claimed that Nezuko's family possessed the Blue Spider Lily.
It was said that the Kamado family had unknowingly eaten the very flower Muzan had been searching for over four hundred years, treating it like a wild plant—thus allowing her to become a "day-walking demon."
However, this theory was later debunked. The Blue Spider Lily only blooms for a very short time each year—just a few days, and only for about ten minutes during daylight.
It was also clearly stated that Tanjiro had only seen it once by pure coincidence while accompanying his mother to visit a grave.
Therefore, whether Nezuko's resistance to sunlight is related to the Blue Spider Lily remains uncertain.
Another theory suggests that because the Kamado family inherited Sun Breathing in the form of the Hinokami Kagura, their bodies underwent subtle changes, allowing the siblings to retain resistance to sunlight even after becoming demons.
There is also a more idealistic theory—
Because Nezuko never consumed human blood, her power came from protection rather than taking from others. She even recovers through sleep, so perhaps the sun itself does not reject her.
But regardless of which theory is true, Shirakawa doesn't know—and he has no intention of taking that risk.
Feeding Nezuko blood might awaken her sooner and create a bond between them.
But it could also ruin her chance of becoming a day-walking demon.
Rather than gambling on that just to bind her to his side two years earlier,
He ultimately decided to let Nezuko develop according to her original path.
At the very least, the overall direction must remain unchanged.
This would serve as the key to obtaining a perfect Vampire bloodline in the future.
If he could truly achieve this goal,
Then with his power, he could reshape—or even control—this country according to his own preferences.
Spending a century he wouldn't even care about to turn it into—
A paradise-like kingdom that belongs only to him, filled with passionate actresses and fiery manga artists!!!
But before reaching that dream…
Everything still depends on strength!
Shirakawa pinched Nezuko's soft cheeks into an even rounder shape and said happily to the system,
"Extract the newbie reward!"
In the next moment, a flood of memories surged into his mind, and a pitch-black long blade suddenly appeared in his hand.
Feeling the increasingly clear knowledge of Basic Swordsmanship in his mind, Shirakawa drew the Soul-Nurturing Nichirin Blade granted by the system with remarkable skill.
He casually performed a flourish.
Nothing around him changed—
Except for three neatly cut strands of hair that appeared on the blade.
Shirakawa's eyes filled with satisfaction.
Basic Swordsmanship was indeed… basic.
No unnecessary flourishes, just pure and precise control.
No fixed forms or techniques, yet it allowed him to wield the sword as naturally as his own fingers.
As for this sword…
It was not an ordinary katana.
Though similar in appearance, anyone familiar with swords could tell the difference at a glance.
A katana's blade and spine are both curved, making it ideal for slashing but unsuitable for thrusting.
But the sword in Shirakawa's hand had a straight spine—running all the way to the tip without the slightest curve.
A horizontal sword!
The ancestor of the katana!
Its straight blade made thrusting easy, while still allowing effective slashing. Its thicker spine also made it more suitable for dealing with heavily defended enemies.
Of course, in terms of killing demons at this stage, a katana—designed for efficient decapitation—was still more practical.
However, katanas have a fatal weakness.
To maximize cutting ability, their edges are ground very thin, making the blade fragile—sharp, but prone to bending, chipping, or breaking.
That's why in many battles, a single strike might decapitate a weak enemy—
But against stronger opponents, the blade could break, forcing Demon Slayers to continue fighting with damaged weapons.
The horizontal sword didn't have this issue.
With its thicker spine and sturdier structure, it was far less likely to break.
Just this alone would make "Sword-Breaker Tanjiro," who goes through blades constantly, green with envy.
It would also leave the swordsmith with no outlet for his frustration.
Of course, whether it breaks or not doesn't really matter.
The system already stated—
This weapon is custom-made: unbreakable, unbendable, and everlasting.
More importantly, Shirakawa liked it for one simple reason.
It looked cool!
That's all that mattered!
Compared to the slender, curved katana, this straight-bladed sword felt far more in line with his aesthetic.
Holding the hilt with one hand and raising the blade before his chest, Shirakawa took a deep breath—
Color Breathing Style, activate!
In the next moment, a faint pink hue began to rise from the base of the blade. Blending with its snowy-white brilliance, it gradually turned into a mysterious purple-pink glow.
Eerie…
Mysterious…
Flashy!
Shirakawa narrowed his eyes as he admired it.
A solemn, dignified sword form combined with a dazzling purple-pink blade…
I love it so much~~~~
And that… wasn't all!
As the system's first reward—and the most important partner that would accompany Shirakawa throughout his life—
This sword was far from ordinary.
According to the system, it was tailor-made based on the Breathing Style awakened by its wielder.
It possessed a unique trait.
If he used Water Breathing, the blade might embody flexibility and adaptability—flowing like water yet sharp as ice.
If it were Flame Breathing, it might carry burning heat with every strike, similar to a Crimson Blade.
Thunder Breathing—perhaps lightning-fast paralysis.
Insect Breathing—possibly built-in toxins.
Shirakawa didn't know the exact details of each.
But one thing he could confirm—
The trait belonging to his Color Breathing Style was—
Soul-Nurturing!