The void between life and death was supposed to be peaceful. At least, that's what Kazuki Yamada had expected when the truck hit him. Instead, he found himself floating in an endless expanse of white, face-to-face with something that could only be described as a cosmic entity.
"Kazuki Yamada, aged twenty-three, dead from vehicular manslaughter," the being stated matter-of-factly, its form constantly shifting between shapes. "Quite the mundane end for someone who spent their entire life consuming fiction about reincarnation, wouldn't you say?"
Kazuki would have laughed if he had a body. "I guess the universe has a sense of irony."
"Indeed. However, your case is... special. Your soul possesses an unusual adaptability, a malleability that makes you perfect for a little experiment of mine." The entity's form solidified into something vaguely humanoid. "I'm offering you a second chance, Kazuki. Reincarnation into another world, with a little gift to help you along."
"Let me guess," Kazuki replied, his consciousness somehow managing to convey skepticism. "Another world, probably one I know from anime or manga, and the 'gift' comes with a catch?"
"Perceptive. The world is one you're familiar with—High School DxD. As for the gift..." The entity waved what might have been a hand, and suddenly information flooded Kazuki's mind. "I call it the Pandora System. It will grant you abilities, powers, and skills from across the multiverse—anime, cultivation worlds, movies, games, you name it. But here's the catch: you don't get to choose what you receive. The system awards you with random abilities based on your actions, growth, and certain milestone achievements."
Kazuki's excitement warred with caution. DxD was a world of gods, devils, and fallen angels—powerful beings who could level cities. "That sounds both incredibly useful and potentially disastrous. What's stopping me from getting something useless or getting something so powerful it paints a target on my back?"
"The system has safeguards. Early on, you'll receive abilities that are powerful but manageable, things you can grow into. As you become stronger, the system will grant you more significant powers. Think of it as a game with level-appropriate rewards." The entity's voice took on an amused tone. "Besides, where's the fun in starting overpowered? You'd be bored within a year."
"Fair point," Kazuki admitted. "Any other details I should know?"
"You'll be reincarnated as a devil, specifically as the last surviving member of the Marchosias clan—one of the original 72 Pillars. Your family was thought to have been completely wiped out during the Great War, but you'll awaken as the sole survivor, hidden away in your family's sealed estate. You'll have roughly eight years before the events of the main timeline begin, and you'll have no peerage, no political connections, and no support structure."
"Marchosias..." Kazuki searched his memory of the Ars Goetia. "The Great Marquis, depicted as a wolf with gryphon wings and a serpent's tail. One of Solomon's demons, known for being strong, valiant in battle, and having dominion over legions."
"Very good. The Marchosias clan trait is called 'Beast Dominion'—the ability to manifest and control aspects of various beasts, combining their strengths into your own fighting style. It's not as immediately destructive as the Bael's Power of Destruction, but it has incredible versatility and a high ceiling for growth. You can manifest beast characteristics—claws, fangs, wings, enhanced senses, even beast-type constructs made of demonic energy. As you grow stronger, you'll be able to combine multiple beast aspects simultaneously and even create full beast transformations."
"That's... actually pretty incredible," Kazuki admitted. "Versatile for combat, utility, and it fits with the whole 'wolf with gryphon wings' theme."
"Indeed. And here's where it gets interesting—your first system ability will be the Mazoku bloodline from Yu Yu Hakusho. Imagine combining the raw, primal youki of a demon with the beast-focused powers of the Marchosias clan. You'll be unique in a way that no one in the DxD universe will be able to fully understand or counter."
Before Kazuki could respond, the white void began to collapse inward, reality bending and twisting around him. The last thing he heard was the entity's parting words: "Good luck, Kazuki. Try not to die too quickly. I have high hopes for this experiment."
Pain.
That was the first thing Kazuki experienced in his new life. Not the transcendent peace of reincarnation described in web novels, but raw, burning pain that felt like his entire body was being rewritten at a cellular level. It was as if two different powers were fighting for dominance within him—his devil nature and something far more primal.
His eyes snapped open, and he immediately regretted it as dim candlelight felt like stabbing needles. He was lying on a cold stone floor in what appeared to be a grand hall, though one that had seen better days. Marble pillars rose around him, each carved with intricate depictions of wolves, gryphons, and serpents intertwined in battle. Ancient magic circles covered every surface, pulsing faintly with residual power.
System Initializing...
Welcome, Host. The Pandora System is now active.
Analyzing host body... Complete.
Current Status:Name: Kazuki MarchosiasAge: 10 (Devil equivalent)Race: Devil (Mazoku Hybrid)Class: Low-Class DevilClan: Marchosias (72 Pillars)Affiliation: NoneClan Trait: Beast Dominion (Dormant - 15% Awakened)
Congratulations! You have received your starter ability:Mazoku Bloodline (Yu Yu Hakusho) - This ancient demon bloodline grants you access to demonic energy (youki) separate from your devil power. Unlike devil magic which relies on imagination and magical circles, youki is a raw, primal force that enhances physical abilities and can be shaped through willpower alone. Current bloodline purity: 25%. As you grow stronger, your bloodline will awaken further, unlocking additional abilities.
Special Note: Your Mazoku bloodline has begun resonating with your Marchosias Beast Dominion trait. Unique synergies detected. New evolutionary paths available.
Kazuki slowly pushed himself to his feet, his new body feeling both foreign and natural. He was shorter than he'd been, maybe four and a half feet tall, with a lean but wiry build that suggested both youth and a natural athleticism. Stumbling to a nearby mirror—cracked but still functional, held in an ornate frame carved with wolf motifs—he finally saw his new face.
Sharp, predatory features that would definitely mature into something striking, maybe even dangerous. Dark silver hair that fell to his shoulders with streaks of crimson running through it—the signature colors of the Marchosias clan. His eyes were the most startling feature: a brilliant amber with slit pupils that marked his beast heritage, though there were flecks of violet that seemed to pulse with otherworldly energy—evidence of the Mazoku bloodline within him.
When he focused, he could feel it—two distinct sources of power coiling within his body. His devil magic, elegant and structured, waiting to be shaped by his imagination. And beneath it, something wilder, more primal—the youki that burned like liquid fire through his veins, responding not to careful visualization but to pure instinct and will.
And there was a third element, currently dormant but present. His Beast Dominion, the inherited power of the Marchosias clan, waiting to be awakened.
New Quest Unlocked: Survival of the FittestObjective: Survive your first month in the UnderworldReward: Random ability drawFailure: Death (and a very disappointed cosmic entity)
"Well, aren't you just full of motivation," Kazuki muttered, his voice younger than he was used to but already carrying an edge that suggested something dangerous lurking beneath the surface. He turned his attention to his surroundings, years of consuming survival media kicking in.
The hall he was in appeared to be part of a much larger estate. The architecture was impressive—clearly built by nobility with power and wealth. Stone pillars rose to a vaulted ceiling where faded murals depicted great battles, always with a silver-haired warrior at the center, surrounded by spectral beasts. The floor was marble, though covered in dust and debris from years of neglect.
Memories that weren't quite his own began filtering through his consciousness, filling in the gaps of his new identity.
The Marchosias clan had been one of the 72 Pillars, respected for their combat prowess and their unique ability to manifest beast characteristics in battle. They weren't as politically powerful as the Bael or Sitri clans, but on the battlefield, a fully realized Marchosias devil was a terror to behold—combining the strength of bears, the speed of wolves, the flight of eagles, and the ferocity of lions into a single devastating combatant.
During the Great War, the clan had been at the forefront of many battles, their Beast Dominion making them natural warriors. But that had also made them targets. A coordinated assault by angels and fallen angels had decimated the clan's main forces. The final blow had come when the clan head, Kazuki's grandfather, had fallen in single combat against a Seraph.
The survivors had retreated to the clan estate, only for it to be sieged. Rather than surrender, the remaining Marchosias had activated the estate's ultimate defense—a sealing barrier that would protect the grounds but also cut it off from the rest of the Underworld. They'd hoped to wait out the war, to preserve at least some of the bloodline.
They'd succeeded, technically. The estate had been sealed, protected by layers of barriers so powerful that even Satan-class beings couldn't break through without significant effort. But the cost had been enormous—the barriers slowly drained the life force of those inside to maintain themselves. One by one, the Marchosias had died, sacrificing themselves to keep the estate hidden and protected until the war ended.
Kazuki was the last. The youngest member of the clan, he'd been placed in magical stasis to preserve his life while the barriers consumed everyone else. And now, years after the war had ended, the barriers had finally exhausted their power reserves, and the stasis had released him.
"So I'm literally the last Marchosias," Kazuki said aloud, his voice echoing in the empty hall. "The sole survivor of a Pillar clan, with no allies, no resources beyond what's in this estate, and no idea if the outside world even remembers that my family existed."
He couldn't help but laugh, dark humor bubbling up. "Well, I've read worse starting scenarios. At least I have a house."
New Quest: Heritage ReclaimedObjective: Explore the Marchosias Estate and secure valuable resourcesReward: Partial Beast Dominion awakeningTime Limit: None
That was more like it. Kazuki began exploring systematically, his new devil senses far sharper than his human ones had been. He could see clearly in the dim light, hear the faint sounds of the estate settling, even smell the age and dust that permeated everything.
The estate was massive. The great hall connected to multiple wings—living quarters, training grounds, a library, workshops, and what appeared to be a treasury vault. Most rooms showed signs of the clan's final days: hastily abandoned belongings, weapons left on racks, family portraits staring down at empty rooms.
But it was the library that drew Kazuki's attention first. Knowledge was power, and if he was going to survive, he needed to understand both his devil abilities and this world better.
The library was impressive—three stories of bookshelves filled with tomes on magic theory, combat techniques, devil history, and most importantly, detailed records of the Marchosias clan's Beast Dominion ability.
Kazuki pulled down a leather-bound tome titled "Beast Dominion: A Comprehensive Guide for Marchosias Heirs" and began reading.
Beast Dominion is the inherited trait of the Marchosias clan, passed down through blood from the original Marquis Marchosias himself. Unlike other clan traits that manifest a single specific ability, Beast Dominion is adaptive and growth-oriented, allowing the user to channel the characteristics of various beasts.
At its most basic level, a Marchosias devil can manifest simple beast features—claws, enhanced senses, limited physical enhancement. As the ability develops, more complex manifestations become possible: wings for flight, armored hide for defense, venomous fangs, echolocation, and more.
Advanced practitioners can combine multiple beast aspects simultaneously, creating unique combat forms. The clan head, at his peak, could manifest twelve different beast characteristics at once, making him effectively a chimera of devastating power.
The key to mastering Beast Dominion lies in understanding that it's not simply transformation magic. You are not becoming a beast—you are manifesting the CONCEPT of various beasts through your devil power. This means the limitations are based on your imagination, magical reserves, and the depth of your understanding of each beast you wish to channel.
Training Regimen:1. Physical conditioning—Beast Dominion enhances your body, but it requires a strong foundation2. Study actual beasts—the better you understand an animal's biology and behavior, the more perfectly you can manifest its traits3. Gradual integration—start with single features, master them, then add complexity4. Combat application—theory means nothing without practical experience
Kazuki closed the book, his mind racing. This was perfect. Beast Dominion wasn't just a single powerful technique—it was a framework for growth that could evolve with him. And combined with his Mazoku bloodline's youki, which enhanced physical abilities and responded to instinct rather than complex visualization, the synergies were obvious.
Devil magic required imagination and visualization. Beast Dominion required understanding of beasts and their characteristics. Youki required instinct and will. Combined, he could create a fighting style that no one in this world would be prepared for.
But first, he needed the basics.
Kazuki spent the next several hours exploring the rest of the estate. In the training grounds, he found weapons of all types—swords, spears, axes, claws, all sized for various users. He selected a simple training sword and a pair of clawed gauntlets that fit his young hands surprisingly well.
The treasury vault was sealed with blood-locked magic, but as the last Marchosias, his blood was the key. Inside, he found the clan's accumulated wealth: gold coins, magical artifacts, precious gems, and most importantly, several communication devices and documents that proved his identity as a Pillar clan member.
The wealth was substantial—easily enough to live comfortably for decades. But Kazuki knew money wasn't his main concern. Power was. In the Underworld, respect came from strength, and he currently had very little of it.
In the clan head's personal chambers, he found the most valuable treasure of all: a complete set of journals documenting training methods, political insights, and combat experiences spanning centuries. The final entry was from his grandfather, written just before the estate was sealed:
"To whoever reads this—if you're reading it, you're likely the last of our bloodline. The Marchosias name once commanded respect and fear. We were warriors, proud and strong. Do not let that legacy die with the estate.
Our Beast Dominion is not a curse or a burden—it is a gift. We are the bridge between civilization and primal power, between the structured magic of devils and the raw instinct of beasts. Master this power, and you will have no equal in single combat.
But remember: strength without wisdom leads to destruction. The Marchosias fell not because we were weak, but because we fought without consideration for politics or consequence. Be smarter than we were. Be stronger than we were. Be better than we were.
Make the name Marchosias something to be feared and respected once more.
— Lord Malphas Marchosias, 73rd Clan Head"
Kazuki carefully closed the journal, a weight settling on his shoulders. He was alone, yes, but he wasn't starting from nothing. He had a legacy, resources, and time. Eight years before canon began. Eight years to turn himself from a weak child into someone who could stand among the supernatural world's elite.
He returned to the training grounds, sword and gauntlets in hand. It was time to start.
Quest Updated: Heritage Reclaimed - Treasury SecuredBonus Objective: Begin Beast Dominion Training
Kazuki stood in the center of the training ground, closing his eyes and focusing inward. He could feel his devil magic, a reservoir of power waiting to be shaped. Beneath it, his youki burned with primal intensity. And threaded through both, dormant but present, was his Beast Dominion.
Following the manual's instructions, he focused on the simplest manifestation—wolf claws. He pictured them clearly: sharp, curved, designed for tearing and gripping. He fed devil power into the visualization, feeling the magic respond.
His hands began to change. Dark energy coalesced around his fingers, solidifying into wickedly sharp claws that extended four inches past his fingertips. They were translucent, made of crystallized demonic energy, with a silver sheen that marked them as distinctly Marchosias.
Skill Acquired: Beast Manifestation (Novice) - Wolf ClawsYou can now manifest basic beast characteristics. Current options: Wolf Claws. Cost: Low. Duration: Limited by focus and magical reserves.
Kazuki stared at his transformed hands, a wild grin spreading across his face. It had worked. The claws felt natural, like they'd always been part of him.
Then he tried adding youki to the mix.
The claws immediately changed, the translucent silver taking on a darker, more solid appearance. Purple-black energy crackled around them, and when he slashed at a training dummy, the claws tore through it like paper, leaving deep gouges that smoked faintly.
Unique Skill Created: Youki-Enhanced Beast ManifestationBy infusing your Beast Dominion with youki, you create beast constructs that are both more durable and more destructive than normal. Current efficiency: Poor. Warning: Excessive youki infusion may destabilize manifestations.
As if to prove the point, the claws suddenly flickered and dispersed, the youki overwhelming the careful structure of the devil magic. Kazuki felt the backlash—a sharp pain in his hands as the energy recoiled.
"Note to self: balance is key," he muttered, shaking out his hands. But despite the failure, he was grinning. This was it. This was the path forward.
He spent the rest of the day practicing, alternating between pure Beast Dominion manifestations and carefully adding small amounts of youki to enhance them. Progress was slow and painful—every failure meant backlash, every success was followed by exhaustion.
But by the time exhaustion finally forced him to stop, he could consistently manifest wolf claws and maintain them for several minutes. More importantly, he could add just enough youki to strengthen them without causing destabilization.
Level Up! You are now Level 2Stats increased. New skill slots available.
Skill Proficiency Increased:Beast Manifestation (Novice) → Beast Manifestation (Beginner)Youki Manipulation (Novice) → Youki Manipulation (Beginner)
Kazuki collapsed onto a training mat, his body aching but his spirit soaring. This was real. The system, the powers, the potential—all of it was real.
He pulled up his status screen mentally, examining his current capabilities:
Name: Kazuki MarchosiasAge: 10Race: Devil (Mazoku Hybrid)Level: 2Class: Low-Class Devil
Attributes:Strength: 15Endurance: 14Agility: 18Magic: 22Willpower: 25
Abilities:- Mazoku Bloodline (25% Awakened)- Beast Dominion (18% Awakened)- Youki-Enhanced Beast Manifestation (Unique)
Skills:- Devil Magic (Beginner)- Beast Manifestation (Beginner) - Wolf Claws- Youki Manipulation (Beginner)- Hand-to-Hand Combat (Novice)
Clan Trait: Beast DominionDescription: Manifest and control aspects of various beasts, combining their strengths. Current mastery allows for single beast feature manifestation. Growth potential: Extremely High.
It wasn't much. By Underworld standards, he was barely worth noticing. But it was a start. And he had time, resources, and a plan.
Over the following weeks, Kazuki established a routine. Wake at dawn, physical conditioning for two hours—push-ups, running through the estate grounds, weapons practice. Then magical training—devil magic theory and practice, focusing on the basics until they became second nature. Afternoons were dedicated to Beast Dominion, learning to manifest and maintain different beast features. Evenings were for youki training and studying the journals left by his ancestors.
The estate became both his home and his training ground. He learned its every corner, discovered hidden rooms and forgotten caches of supplies. The magical defenses slowly regenerated now that they weren't being used to maintain the barrier, meaning he had protection if anything tried to intrude.
Progress was incremental but steady. By the end of the first month, he could manifest not just wolf claws, but also enhanced senses—the keen hearing of a wolf, the sharp eyesight of an eagle, the scent-tracking ability of a bloodhound. Each new manifestation required study, practice, and countless failures before he achieved stability.
Quest Completed: Survival of the FittestReward: Random ability drawProcessing...
Congratulations! You have received:Enhanced Regeneration (Prototype) - Your body heals faster than normal devils, recovering from minor wounds in minutes and major injuries in hours. This ability will grow stronger with use and training.
Note: This ability synergizes with your Beast Dominion. Many beasts have enhanced healing. Integration opportunities detected.
Kazuki tested the new ability immediately, deliberately cutting his palm with a training knife. He watched, fascinated, as the wound closed within two minutes, leaving only a faint pink line that faded completely within five.
"That's going to be useful," he said, already thinking about how to combine rapid healing with aggressive combat styles. If he could recover from injuries mid-fight, he could take risks that would cripple normal fighters.
But his time in isolation couldn't last forever. The estate was secure, yes, but it was also cut off from the rest of the Underworld. Sooner or later, he'd need to make contact with devil society, establish his identity as the Marchosias heir, and begin navigating the political landscape.
The question was: when? He was still weak, still learning the basics of his powers. Revealing himself too early would make him vulnerable. But waiting too long meant missing opportunities to build connections and gather information about the current state of the Underworld.
New Quest: EmergenceObjective: Make contact with devil society and establish your identity as the last MarchosiasReward: Random ability draw + Political contactRecommended Level: 5+Note: This is a high-risk, high-reward quest. Prepare carefully.
Kazuki stared at the quest notification, then at his current status. Level 2, barely competent with his abilities, and facing a world where ultimate-class devils and Satan-class beings existed.
"Guess I've got work to do," he muttered, then returned to training with renewed intensity.
The game had begun, and Kazuki Marchosias was just getting started.
End of Chapter 1