DxD: Delusion X Fantasy

Kaien Akagiri lay lazily on the bed of his dimly lit room, the faint glow of his desk lamp casting long shadows against the walls.

In his hand, he toyed with a small glass vial filled with a swirling, crimson liquid.

One of the perks of being reincarnated into your OC was that you didn't have to deal with the responsibilities of a regular person.

In Kaien's case, this meant that this new body had no attachments, yet he was somehow able to live by himself.

Kaien Akagiri lived alone, which wasn't exactly shocking—he was an orphan, after all, never mind the fact that a kid his age shouldn't be able to afford to live alone in the first place.

In a world like this, it seemed almost expected.

Parents in these kinds of settings had a funny habit of being dead, conveniently absent, or blissfully unaware of the chaos their children were involved in.

If anyone asked, his solitary lifestyle was just another checkbox on the "mysterious loner" archetype list.

The fact that it also provided the perfect cover for his magical abilities? Well, that was just a happy coincidence.

And he had transfer student privileges, why a random orphan could transfer to kuoh he'd never know, but it worked so he didn't think about it too much.

Kaien's home was modest, unremarkable at a glance—a single bedroom and bathroom, a small living room that doubled as a kitchen, and one spare room that served as his mage's workshop.

The layout was simple, efficient, and entirely ordinary to anyone who might stumble upon it.

But beneath the surface, it was anything but.


The workshop was the heart of the house and the one place where Kaien's true self was laid bare.

Layered with all manners of bounded fields—ranging from offensive and defensive measures to concealment and alarm triggers—the workshop was Kaien's private sanctuary, hidden away from the world.

Every barrier, rune, and ward were painstakingly constructed to shield his work from prying eyes, magical interference, or even an accidental discovery by someone curious enough to wander too far.

Even the members of the Occult Research Club, who thought they knew Kaien well, were unaware of its existence.

it was a mostly utilitarian space, sparsely furnished save for the essentials: a large wooden desk scarred with burn marks and knife cuts, shelves lined with books and scrolls on everything from runes to curses, a corner dedicated to jars of reagents and finally a few mystic codes that had come along with him into the world.


While the entire house did technically function as a workshop of sorts, Kaien had typically confined his experiments to this single room.

Here, he practiced magecraft, refined his spells, and pushed the limits of his skill, Territory Creation.

At its current lowly rank of E, it was nowhere near what he aspired. It was said that magi from the age of gods could craft entire domains: temples brimming with power, expansive workshops that gathered mana effortlessly, spaces that warped reality itself, or even a flying castle.

But for now, Kaien could only muster a small, rudimentary sanctuary. His current workshop was functional but modest—just enough to collect a meagre amount of ambient mana and provide personal protection from external interference.

Kaien dreamed of expanding it, turning his humble workshop into something more fitting of a true magus.

Perhaps one day, with enough practice and a higher rank in Territory Creation, he could craft a space worthy of the title.

For now, though, he would make do.

The rest of the house was unremarkable. His bedroom contained barely more than a bed, a small closet, and a desk.

The living room was dominated by an old couch and a shelf filled with books—half were mundane and borrowed from the school library, while the rest were books on magic from this world given to him by Rias.

The kitchen was a cramped afterthought, though the pantry was stocked with instant meals and the occasional treat.

It had only been a few months since his arrival, but he really needed to find time to decorate the place.

Then again, he wasn't sure how long he'd be staying.

Kaien's stomach suddenly growled, breaking the silence of the dimly lit room. He sighed and sat up, putting the vial of red liquid back in his pocket.

For all his magical talents and reincarnated foresight, hunger was still a problem he hadn't found a convenient way to solve.

It was inefficient, If he could solve issues like sleep and hunger, he could spend more time researching magic.

Sure, he could have opted to be reincarnated as a devil or some other supernatural being, but that option had its own set of unknowns.

Besides, he wasn't entirely certain whether devils even needed to eat to survive.


He'd seen Rias and her peerage indulging in meals plenty of times—lavish dishes that suggested they definitely enjoyed the act of eating. But was it a necessity for their survival? That was still up in the air. 


For all he knew, devils might simply subsist on magic, their bodies sustained by the power that coursed through them. 


On the other hand, if devils really did need to eat to survive… well, the mental image of the all-powerful Sirzechs Lucifer, the mighty king of hell, keeling over from something as mundane as starvation was… amusing, to say the least.

Making his way to the kitchen, the faint creak of the wooden floorboards accompanied his footsteps.

The pantry, as always, was a depressing sight—instant noodles, canned soup, and a few bags of chips.

His culinary prowess was as unremarkable as his mundane life appeared to be the average outsider.

Grabbing a packet of noodles, he filled a pot with water and set it on the stovetop.


With a spark, he felt his circuits ignite and with a flick of his finger, the gas stove lit up, the small flame at his fingertip vanishing as the burner lit.

It was funny, really.

Magecraft had the potential to deceive the laws of reality, yet here he was, still reliant on a gas stove to cook a meal.

It didn't really match the image of grand magus he had going for himself in his head, but he was working on it.

"Some genius magus I am," he chuckled to himself, a wry smile tugging at the corner of his lips.

While Kaien was learned in a few fields of magecraft, elemental magic wasn't one of them.

He knew the basics—enough to get by—but it wasn't something he'd invested much time in. Instead, he'd pushed it aside in favour of practices he found far more useful.

Curses, runes, familiars, bounded fields—among others, these were the areas Kaien had spent most of his time researching and mastering.

They weren't the most offensive practices, but where they truly shone was in their utility and versatility. 

Taking the time to incant a spell for a fireball to shoot at a stray devil? Foolish.

That wasn't even considering the fact that the same devil could probably do it faster, with just a thought and a simple magic circle.

Standard magecraft just didn't hold up against the supernatural forces of Draconic x Deus, so Kaien improvised. It was why he'd convinced Kiba to teach him the way of the sword.

Of course, when he did need firepower, he had something far more potent than standard fireballs. Flames that could give even a devil a serious run for their money.

That said, Kaien wasn't entirely sure how he felt about using cursed fire for cooking.

"How would food cooked using cursed flames even taste?" he muttered, shaking his head at the thought. It probably wasn't the healthiest of cuisines.


Eventually, the Noodles finished cooking and Kaien poured the noodles into a bowl, the steam rising as he added a dash of seasoning.

Kaien slurped up the noodles in the silence of his apartment. It wasn't exactly gourmet cuisine, but it filled the void well enough.

He grabbed a glass of water, washing down the meal before slurping the last of his noodles and setting the bowl down on the counter with a satisfied sigh.

Tossing the empty bowl into the sink, Kaien's gaze drifted to the hallway that led to his workshop.

It was time to get back to work.

Kaien wiped his hands on a dish towel, flicked off the kitchen light, and made his way to the room that served as the heart of his little domain.

The air seemed to change as he stepped through the doorway.

Where the rest of the house felt mundane and ordinary, the workshop was different—charged with an energy that made the hair on the back of his neck stand on end.

Kaien approached his cluttered desk. The glow of a lamp illuminated books stacked haphazardly, jars of reagents and tools scattered across its surface.

Kaien sat down, reaching into his pocket, and took out the red vial. The crimson liquid swirled inside, moving like it had a mind of its own.

The Idea Replica.

Kaien picked it up carefully, holding it to the light. The liquid inside shimmered unnaturally, moving almost as if it were alive. And in a sense, it technically was.

Liquidised conceptual blood of unknown origin—a crystallised essence of a principle so potent it could transform the very nature of the one who consumed it.

It was a special drug created by Dr. Arach in the Tsukihime series, and as far as he knew, was derived from the essence of another Dead Apostle's Idea Blood, a core principle that defined their existence and powers.

Injecting it could turn someone into a Dead Apostle, enhance the rank of an existing one, and sometimes even allow them to inherit the unique abilities tied to that Idea Blood.

Kaien's vial, however, was different. He didn't know whose Idea Blood it contained—or if it even belonged to another Dead Apostle at all. For all he knew, it could be something completely original.

What he did know was that injecting it would change him irreversibly, crossing the threshold from human to Dead Apostle.

He set the vial back down on the desk, his gaze flickering to two empty spots on the nearby shelf—places where two other items should have been.

Their absence gnawed at him like a splinter in his mind.

It seemed that whatever cosmic force that had sent him to this god forsaken world was nice enough to carry along his 'build with him'.

A genius ability at magecraft, a home, some mystic codes and an identity were all given to him when he woke up in kuoh one morning a few months ago.

The idea replica and his other items had all been waiting in his workshop for his use.

Along with the Idea Replica, there were some black keys to deal with those pesky devils, rule breaker to cheat those pesky devils and a couple performance enhancing mystic codes to beat those pesky devils.

However strangely enough there were two items missing.

The first missing item was a vial of Dragon Blood, a potent magical substance that could have enhanced his human physique and dramatically increased his capacity for mana.

It was meant to serve as a backup plan—an alternative to the Idea Blood if he decided against becoming a Dead Apostle.

Or at least serve as a pathway to ease the process. After all, having Dragon Blood would definitely help in the potentially lethal act of injecting a Dead Apostles Idea Blood into his system.

With its help, he could have elevated his physical and magical abilities significantly, without necessarily crossing into inhuman territory.

The second missing item was far more concerning.

The Holy Grail.

A treasure coveted by magi across every era, the Grail was a condensed mass of pure magical energy.

It was an artefact capable of reacting to the wishes of its holder, potentially granting them anything their heart desired.

The Grail could've served as an unparalleled magical battery, its limitless capacity allowing it to power even the most ambitious spells and rituals.

It could enhance a magus's abilities exponentially, acting as a catalyst for miracles.

Kaien had envisioned countless uses for it.

He could have stored excess magical power within it, used it to stabilize the transformation process of the Idea Blood, or summoned Servants from the Throne of Heroes.

The possibilities were endless, and its absence was a massive setback.

The Grail was meant to be his failsafe. His final trump card.

A vessel of near-infinite mana that could stabilise his experiments and fuel his ambitions. Its absence left a gaping hole in his plans.

"What happened to it?" Kaien muttered, staring at the empty spot on the shelf.

The Grail and the Dragon Blood should have been here, the the other tools and mystic codes were but they were suspiciously absent.

The whole thing was incredibly inconvenient and more than a little suspicious.

If someone else had managed to get their hands on them?

The very thought gave him some pause and only became more frightening the more he thought about it, so he decided not to and do everything he could without them.


The Chaos Brigade with a Heroic Spirit army…

He shivered.

For now, though, there was nothing he could do about it. He'd scoured his workshop and even tried to trace the Grail's magical signature, but it was as if it had vanished entirely.

Kaien turned his attention back to the desk, his fingers brushing over the vial of Idea Blood. This was the one item that remained, the cornerstone of his ambitions. 


With Rias's announcement of the fallen angels, it meant that the chance for him to use it was fast approaching.

It was dangerous—he knew that—but it was also his best shot at levelling the playing field.

There was still one more thing to do before his plans could begin.

Kaien shifted his focus back to the desk, his eyes landing on a worn grimoire resting atop the clutter. Its cover was marred with age.

The book was opened to a bookmarked page—familiar creation.

His finger traced the words etched into the paper, the intricate diagrams and arcane notes detailing the process.

Familiars were one of the more versatile tools in a magus's arsenal. There were several ways to create them, but most methods were rooted in a common theme: the use of corpses.

The standard practice involved taking the soul of a deceased human usually through a body part such as hair and fusing it with the body of an animal.

The result was a wholly new existence, independent of both the human soul and the animal body.

These familiars were strong, loyal, and—most importantly—capable of operating without constant oversight.

Kaien had experimented with the process before, though with mixed results. Without a properly attuned soul, the familiars he created were little more than mindless constructs, bound entirely to his will and incapable of acting on their own.

They were functional but lacked the independence and adaptability that came with a true familiar. They weren't the most powerful creatures, but suited his needs just fine.

There were alternatives, of course.

He could summon daemons to act as familiars, but that was a dangerous and inefficient route.

Summoning and binding a daemon required significant magical resources, and the risks outweighed the rewards in most cases.

But Kaien didn't need to do all that.

Not yet.

For now, he'd rely on simpler constructs, ones that didn't require the use of a soul.

Birds would be ideal—light, fast, and capable of traversing areas that would be too dangerous or inaccessible for him to scout himself.

These birds wouldn't be fully autonomous, but they would obey his commands without question, and he'd be able to share his senses with them.

"Let's see if this works better than last time," he muttered, pulling a piece of chalk from the desk.

"Hopefully, I don't blow this place up again," Kaien muttered under his breath, glancing at a scorch mark in the corner of the room.

The soft scrape of chalk against stone filled the room as he redrew the magic circle. Lines, runes, and sigils came together, forming a complex array.

This time, he refined the design, adjusting the runes to better attune the circle to the nature of the familiars he wanted to create.

With the magic circle complete, Kaien straightened up, brushing the chalk dust from his hands.

He stepped into the back of the workshop, where several tools and materials lay neatly organised—or at least, as neatly as someone in his line of work could manage.

He returned moments later, carrying a small box. Inside were the corpses of a few birds—sparrows, mostly, collected from a mix of scavenging and "borrowing" from nature.

He placed the box down beside the circle and carefully pulled each one out, arranging them in the centre of the array.

The sight didn't bother him. This wasn't the first time he'd worked with corpses, and it certainly wouldn't be the last.

The smell, however, was another matter.

Kaien wrinkled his nose as he set the last bird down, muttering under his breath, "I really need to figure out a way to mask that."

Kaien took a deep breath, steadying himself. His mind focused on the image of a spark—a single flicker of potential that grew into a roaring bonfire.

He felt his magic circuits ignite, the hum of power coursing through him as he placed his hand on the circle.

The circle flared with light, the runes glowing brighter, the air grew thick with mana, pressing down on him like an invisible weight.

The corpses began to twitch, their forms shifting and warping as the spell took hold.

Feathers turned dark as shadows, shimmering with an unnatural sheen, and their eyes burned red with a faint, ghostly glow. One by one, the birds rose to their feet, their movements fluid and silent.

Kaien lowered his hand, watching as the familiars stretched their wings and flitted about the room.

They weren't true familiars—no soul had been used in their creation—but they were perfect for reconnaissance. Fast, agile, and disposable.

One of the birds landed on his shoulder, its glowing eyes meeting his. Kaien reached up, running a finger along its shadowy head.

It didn't feel like flesh or feathers—more like the smooth surface of glass.

"Good," he muttered, a small smile tugging at his lips.

With a mental command, the familiars dispersed. They took to the air, their forms flickering like wisps of shadow as they passed through the room's bounded fields. Kaien stood there for a moment, watching the last one vanish.

"Let's see what you can find," he said quietly, turning his attention back to his desk.

Finally.

This was it.

All that was left now was to make his move—and hope the gamble paid off.