DxD: Fusion

1 week into winter break

Toshio Perspective

The air carried a morning crispness, a faint chill that hinted at the changing season. Dew glistened on the grass like beads of glass, and somewhere in the distance, a bird sang a lazy tune. My breath puffed faintly in the cool air as I raised my hand, palm glowing with an icy shimmer.

The clearing itself was nothing special—just a patch of wild grass hemmed in by birch and pine, the ground uneven from generations of burrowing rodents and weather-worn roots. But it was private, and more than that, it was mine. A small animal-like yawn was heard. Okay maybe her's too.

One last push.

I sat on the ground, frost gathered at my fingertips. A faint blue corona shimmered around my hand. The magic circle pulsed, growing more dense, the glyphs crowding inward toward a singularity. I could feel the cold sinking into my bones as ambient water vapor condensed around my hand, freezing solid in bands of thin, icy air.

"Create Frost."

A cold burst formed in my palm—a weak cone of frigid air barely enough to frost the grass in front of me. But it shimmered with clarity, stable and sharp. Rank 10 at last. The moment it completed, the magic circle flickered and dissolved into faint snowdust, and the air around me seemed to still.

A familiar tone rang out in the background, a soft chime echoing across my HUD.

{Quest Complete! Master the Basics: Get all basic elemental Create spell skills to Rank 10 within 14 days.

+2,500 XP

New Skill Unlocked! Spell Creation (Rank X)}

A second, sharper chime followed as the quest window faded, replaced by a soft golden glow that pulsed once over my skill list. A sense of mental clarity washed over me, like someone had just tuned a foggy radio into perfect signal.

{Spell Creation (Rank X): A foundational spellcrafting skill that allows the user to design and cast original spells from scratch. Because it exists beyond conventional limits, its growth is tied not to rank, but to the creator's intellect, creativity, and magical aptitude. The more complex the user's understanding of magical theory, elemental properties, calculations, physics, and runic orientation, the more potent and innovative their creations can become. This skill cannot be ranked up—only mastered through insight and practice.}

I exhaled sharply, blinking as the realization slammed into me.

"Wait. Spell Creation?"

A grin pulled at the corners of my mouth before I could stop it.

I hadn't expected this. I thought I was either on my own or had to read/consume more grimoires.

This changed everything.

I stood up without thinking, hands already moving as I conjured the old rune for Create Flame. The original version, the one that barely sputtered. Then, like flipping a mental switch, I layered in the lattice of what I'd just learned—the math, the matrix, the ratios of heat to mass compression. The symbols shifted under my fingers like obedient keys. My thoughts poured into the structure like fuel.

I could do this. I could alter spells. Modify them. Iterate.

This wasn't just a new skill.

It was an entire forge.

Finally.

Each of the elemental creation spells had been frustratingly weak, barely offensive in any meaningful way. Create Flame, Create Spark, Create Frost… they were little more than glorified elemental lighters, each one a shallow mimicry of the real thing. But that wasn't the point.

The point was what came after. This.

Until now, creating original magic had felt like trying to build a reactor with no blueprints, using scraps from old cans and chewing gum. I had theory. I had ambition. But nothing stuck. Nothing moved. The framework was alien, like trying to code in a dead language without a compiler.

Now though, it felt different. Like I finally understood the shape of the language. Not fluency—not yet—but recognition. The grammar. The sentence structure. What used to feel like chaos now shimmered with potential. My mind started forming equations and circular rune matrices with frightening ease. It was as if the system had finally handed me the Rosetta Stone.

Kuroka was curled up under the late morning sun just a few feet away, tail flicking in her sleep. Her cat form stretched lazily across a small, elevated stone platform I had conjured for her a few days ago with Create Earth. It sat at the edge of the forest clearing, perfectly positioned to catch the warmest rays all morning.

I wasn't sure why she'd started showing up every day. But I wasn't complaining. Gave me someone to talk to. And who didn't like petting and loving on cats?

And I kept giving her chocolate. It seemed to be a favorite snack.

I dusted frost off my palm and wandered over, crouching at the edge of her little throne. She tensed for a split second, then relaxed, chin resting on her paws. I reached out and stroked behind her ears—deliberately gentle—and was rewarded with a slow-building purr that vibrated through my fingertips.

"Hey, girl," I murmured. "How's the life of luxury treating you?"

She didn't deign to reply, but her eyes narrowed contentedly. For a moment, I felt almost normal. Just a guy in a clearing, petting a cat, with nothing more complicated on his mind than magic. Maybe not the best example.

Her tail curled slightly at my touch.

"You like this spot, huh?" I said quietly. My voice didn't disturb her, but her ears twitched.

Reaching into my pocket, I pulled out a small wrapped square of dark chocolate. Homemade. Melted down, tempered right, dusted with cinnamon. I unwrapped it and held it out.

She didn't open her eyes. Just sniffed once, and then took it in her mouth with elegant precision. Chewed slowly.

"You're getting spoiled, you know," I said, still in that soft, private voice. "If others see how much chocolate you're eating, they'll stage an intervention."

Her tail flicked in silent rebuke. She chewed, swallowed, then licked her lips with slow deliberation.

"Glad you like this homemade batch too," I murmured.

Kuroka's eyes shot open, gold and sharp as obsidian chips. She fixed me with that familiar, unblinking stare, something poised between predation and appraisal. It was comical sometimes, how much her expressions mirrored a real person's. She was a horrible actor.

Slitted pupils widened for a fraction of a second, then relaxed as if nothing unusual had happened at all. I snorted, unable to hide my amusement.

"What, surprised I didn't buy it from the store?" I knelt next to her stone pedestal and tapped the side with two fingers, offering a fresh square.

"I can make more than one kind, you know."

She didn't so much as twitch a whisker, but her eyes didn't leave mine.

"You can come by whenever. Just... meow or something if you want more."

She blinked once.

Then meowed.

It was... not a normal meow. Soft, yes, but smoky. Just a little too slow, too velvety to be mistaken for a real cat. Like someone whispering the idea of a meow while sipping wine.

I blinked. "That's... definitely not normal."

She licked her paw, eyes never leaving mine, and began cleaning the space between her claws with a studied nonchalance. If a cat could smirk, I swear to God, this was it. For all I knew, it was an inside joke in her world: every time some dumb human thought they'd tamed her, she'd just lay on the charm and watch him melt.

I shook my head, laughing softly, and gave her another gentle stroke behind the ears. The vibration of her purr was almost ultrasonic, like the low, sub-bass of a club speaker thrumming through the ground. Satisfied, she rolled onto her side, stretching until her spine arched in an elegant curve.

With a final scratch under her chin, I stood and dusted my hands on my shorts. The air was already warming up—a sign that I'd burned more daylight than intended. I walked back to my casting spot, marked by a trampled patch of grass and a ring of tiny scorched divots from dozens of failed spell attempts.

Time to work.

I summoned the spell circle for Flare again—one of my earliest fire spells. Tennis-ball sized, 30 feet per second, a little burst of fire. I let it hover in the air for a moment this time. Instead of casting, I pulled on the runes.

The circle was simple: four runes, nested triangles, a few notches for timing and power flow. But instead of casting, I willed the circle to stay in place, floating inches above my palm, and then I reached in with my mind and started pulling it apart.

The runes stretched like wires. Mathematical symbols shimmered behind the formation, weaving into the spell's foundation.

I let the math run wild in my head: heat versus mass, expansion rates, arc velocity. The symbols responded, shifting into new configurations as if eager to show what they could do. I layered ratios and feedback loops, re-calibrating for every variable I could think of.

Expand the sigil. Reinforce the mana acceleration lattice. Shift the combustion pressure forward so it wouldn't blow up in my face.

The moment it stabilized, I launched it.

A fireball the size of a volleyball streaked out from my hand, slicing through the air in a perfect arc. It connected with a tree trunk at the far end of the clearing, and detonated with a hollow, thunderous pop. Bark splintered and a cloud of black smoke curled upward in a corkscrew, the smell of charred wood mingling with the earthiness of the morning dew.

I held my breath, waiting for the system notification. Sure enough:

{New Tier 2 Spell Skill Unlocked! Fireball}

Bigger. Faster. Hotter. A volleyball-sized sphere that moved over sixty feet per second and exploded on impact.

Better than expected.

I nodded in satisfaction, watching the lingering smoke curl.

Fireball had promise. But more importantly, the pattern was repeatable.

As with Flare, once a spell reached Rank 5, casting became easier—not just faster, but reflexive. Just a little time for the circle to form. And Rank 10? Double the base power.

This was what I was hoping for. Quick, layered improvements. Base spells to be modified. Modular upgrades. Build a foundation strong enough, and I could evolve and fuse spells.

Right now, fire mattered most. Because fire was one of Ghom's biggest weaknesses thanks to the methane it gave off. 

I glanced toward Kuroka.

Her golden feline eyes were locked on me, wide and sharp. Her mouth hung slightly open, small white fangs peeking between her lips. Heh. Teef.

I raised a brow. "Impressed?"

She shut her mouth quickly, then gave me a look that could only be described as suspiciously feline.

I smirked.

She's not very good at playing cat. Outside of the napping, anyway.

She snapped her mouth shut and looked away, feigning disinterest. But the tip of her tail twitched in a way that betrayed her.

I kept my face relaxed, my tone breezy.

But inside, I was watching her just as closely.

Because I knew. And she couldn't know that I knew.

That name—Kuroka—carried weight. She was dangerous. And dangerous to know. She wasn't just a magical stray. She was something far more tangled. And if I let even a flicker of recognition slip, I might lose whatever strange rhythm we had built here.

She huffed through her nose and curled her tail over her paws. Still watching.

I exhaled, stepping back from the test zone. My muscles were tense from focus.

Sitting down cross-legged, I leaned back on my hands and looked up toward the sky.

Magic.

It all started with her.

Rias.

She was the first to really open that door for me. The one who handed me the grimoire. Who gave me a starting point. And now, with Spell Creation unlocked, I could feel that potential expanding.

She had no idea what she'd started.

I smiled faintly.

I missed her.

It had only been a week since she and the others left for the Underworld, but their absence lingered. I missed Akeno's smug provocations. Rias' elegance and cute reactions. Their presence. Their steadiness.

I thought about what I told Rias before she left.

"By the end of break, I'll be strong enough to kill it."

And I would. This was the first step. Fire.

The next would be speed.

Ghom's second form was fast. Stupidly fast. The kind of fast that made trees blur and limbs disappear mid-swing. I could tank some hits. But I needed to move. I had to contend with that speed.

Which meant it was time to test an idea.

I leaned forward again, eyes narrowing. My mind whirred.

Could magic reinforce my speed?

I extended my hand and conjured a new, empty circle—a blank canvas. My reiryoku flowed into it, slower, more careful. It didn't react yet. The circle was a shell, waiting for definition.

I frowned. What would go in this? Speed? Enhancement?

I remembered something. Akeno formed platforms of magic under her feet to float. The air-step spell. And then something else—One Piece. Moonwalk. Launching from the air with burst force.

My lips twitched.

Maybe it was stupid.

But just maybe, it would work.

XXX

2 weeks into winter break

Kuroka Perspective

This kid—this damn human—was insane.

Not just a little off-kilter, not the usual "ha-ha, humans are reckless and self-destructive, let's mess with them for fun" kind of nuts. No. This one was an outlier, a certified, PhD-level lunatic who didn't just break the rules of magic, he violated them in ways that would make a devil priest faint.

Watching him work was like watching an infant chimpanzee pick a lock to a nuclear missile silo: horrifying, hilarious, and a little bit sexy. And yes, I am allowed to say that. I'm a cat.

At first, I was only watching out of professional interest. It's not every day a stray like me gets front-row seats to forbidden magics and wild innovations. His early control over the elements was already impressive. Most humans spent months just trying to keep a Spark spell from backfiring and setting their hair on fire.

Even devils—proper, noble, arrogant devils—needed weeks to get the hang of basic pyromancy. Toshio? He did it in five days, maybe less, and he made it look like he was just tying his shoes.

I knew he wasn't some trained magician. He didn't have the right aura for it. Too raw. Too untamed. Too... hungry. He wasn't drawing power from ritual or bloodlines or old grimoires. No, this one was figuring it out with pure brainpower and something deeper. I don't even know what to call it. Obsession? Madness? Genius?

My second thought was that he was being taught or groomed by another entity, devil, fallen angle, something. But no. No one visited, he was always alone. Even the previous times I saw him in passing outside of school.

Then came the kicker. The moment he made his own spell. Right in front of me. No paper. No chalkboard. No incantation. Just him, muttering numbers under his breath and waving runes into the air like he was doodling in another dimension.

Minutes.

Not hours. Not days. Minutes.

Do you know how long it takes a normal human to create a spell? Weeks, even for the best of the best. They draw it out, test it, revise it... and half the time it explodes in their face. But him? Toshio—and yes, I figured out his name shortly after he started hanging out with my dear sister, I'm not dumb—he did it like he was rewriting a line of code. Easy. Confident. Natural.

And it pissed me off a little.

But not enough to stop watching.

He'd been at it for a week straight now. This poor forest. Fireballs flying every which way, the trees were getting torched like it was mating season for salamanders. And now he was doing something even more ridiculous. He was trying to use magic circles to speed forward, like a high speed technique. Something every magician would be envious over.

I watched from my sunny stone perch, flicking my tail lazily. He had made it for me a few days ago with that Earth spell of his—just raised a flat, warm slab of stone out of the ground without a word. Perfect height. Perfect angle. Caught the sun from morning until late afternoon.

It was... nice. Thoughtful. I couldn't remember the last time someone just made me a spot like that. I didn't ask. He just did it. Like it was obvious I'd want it.

The first time I saw it, I almost fell off my perch from laughing.

He'd set his spell, braced himself just so, and then—bang—a circle flared under his heel and sent him tumbling feet-over-head into the underbrush. The noise he made on impact was somewhere between a squawk and a curse. He brushed himself off, fixed his hair, then did it again.

Over and over, each time adjusting the output, the angle, the force. Sometimes it worked and he got a little lift; sometimes it misfired and bounced him sideways into a tree. Once, the circle detonated too early and he landed flat on his back, staring at the sky like he was reevaluating every decision that had led him to this point.

I could have watched him for hours. I did watch him for hours.

But also?

Kind of brilliant.

Other than the stupid Khaos Brigade meetings I got dragged to once a week by that depressing guy Vali, this was basically how I spent Kuoh's winter break. Watching him. Since Shirone was off with the Gremorys in the Underworld, I didn't have much else to do.

For a human, he was unusually easy on the eyes. I'll give him that. Even under two layers of sweats and a thermal, his body language said "fighter" more than "wizard." Lean, restless, always moving. When he thought nobody was watching, he'd run through kata or shadow-boxing drills along the creek.

Sometimes, if he was feeling especially ambitious, he'd do pushups with his hands balanced on two spell discs, like a circus act. I tested his limits a few times—jumped on his back mid-set, just to see if he'd break. He never did. Just flashed a sideways grin and kept going, like he was used to carrying extra burdens like they didn't weight anything at all. The thought made my mind go to dark places that I quickly pulled myself out of. 

But even with his shirt on—which was often, unfortunately—his physique was no joke. Lean muscle. Broad shoulders. Definitely someone who trained every day.

It was... annoying that I couldn't get to him. But also kind of impressive. Maybe a little, hot.

And the chocolate.

The chocolate was divine.

I mean, seriously. Where does a wild human learn to make chocolate like that? It couldn't have come from Seven-Eleven, not with the way he tempered it, the way the cinnamon folded in just so, not overwhelming the bitterness but rounding it out. Every time I thought I'd tasted the best batch, he'd show up with something new—a twist of orange zest, crushed nuts, once even a dusting of espresso powder. It was always different, always thoughtful. I'd always liked being fed, but it was extra nice when he did it, for some reason.

As much as it killed me to admit it, Toshio's offerings had started to mean something. Not just because I love chocolate, but because he never expected anything in return. No strings. No deals. Just... kindness.

Had nothing to do with why I was here, obviously.

Totally unrelated.

...Maybe a little related.

And when he pet me—ugh, not that I liked it or anything—it was always in the right spots. Behind the ears, down the spine, right between the shoulder blades. The way his fingers moved, slow and deliberate, it was like he knew. His touch didn't feel cautious or awkward, just warm. Grounding.

The second his hand lingered, I could feel every muscle in my body melt, my breath slowing, tail curling unconsciously around his wrist.

I watched him crash into another tree, and a little snicker slipped out before I could stop it. Tail flicking behind me.

Idiot.

But a fun idiot.

I couldn't help but admire that whenever he made a mistake, he would never get discouraged or give up. He would just keep going like a pillar of resilience. No matter how funny it was.

He did the same with me, too, which was annoying in a way I could never quite scratch. Every time I tested him, he adjusted. Never once flinched or scolded. Never threatened to put me on a leash like a certain highborn devil who will remain nameless. He just gave me space when I wanted it, attention when I didn't, and always seemed to know which was which.

It was infuriating. It was... nice. That last bit was a problem. I flicked my tail in agitation, tried to focus on the magic instead, but the warmth of his hands lingered on my skin like static. Every time I saw him, it was harder to remember why I kept wary of him. I'd known plenty of humans: the afraid, the ambitious, the cruel, the heartbreakingly soft.

They all wanted something from me like my power, my body, my bounty reward. This one never asked, not that he'd know about them. But that still made me want to give. I hated that. But I also kind of loved it. Leaning into it was most likely a mistake. But I couldn't find myself trying to be correct. He couldn't find out who I was. 

Then there was his energy. That was the real mystery. It wasn't mana. I'd stake a whole box of chocolate on it. It wasn't ki either. Too refined. Too... quiet. Most people with spiritual power leak it like a broken hose.

Even strong devils like Rias or my sweet little Shirone, you can sense from cities away if you're trained. But him? This kid was like a sealed well. Deep. Still. Dense. You didn't notice it until you were standing right next to it. And then it hit you. Like pressure at the bottom of the ocean. It wasn't loud. It was heavy.

The first time I brushed my senses against it, it nearly knocked me off the wall. The second time, I tried to probe deeper. Pushed my luck. That was a mistake. The pressure doubled, then tripled, then suddenly I was staring at the dirt, kneeling on all fours with my heart hammering in my chest like I'd glimpsed the inside of a black hole.

Toshio didn't even notice. Or maybe he did, but pretended not to, out of politeness or mischief or something stranger. Either way, it was terrifying. And it made me curious. And curiosity was dangerous for me. Always had been.

I told myself I'd stop watching after the third day. Then I told myself I'd stop after the end of the week. Then after the chocolate ran out. But he kept making more, and every batch was different, and by the time I realized I was making excuses, I'd already come up with five more reasons to stick around. Every night, I'd return to my little abandoned shrine, curl up on the altar, and tell myself I was only keeping tabs for professional reasons.

That I was just doing recon. That I owed it to Shirone to make sure this strange human wasn't out to her or, worse yet, make a mess big enough for the Sitri or Gremory to come sniffing around before Vali executed his plans. Not that I really cared for anything other than my dear sister.

But the truth was, I liked the way his energy made me feel. It was alive and full and hungry, and it made my own aura spark in ways I hadn't felt since I was little. Or at least since the last time I'd been part of a real family.

Sometimes I wondered if I'd gone soft. If I'd been in hiding too long. If maybe, just maybe, I wanted to be needed as much as I wanted to be loved by Shirone.

I watched Toshio set up a new magic array, hands moving with that same infuriating confidence, and felt a pang of something like envy. Or maybe longing. Or maybe both at once, tumbled together like a pair of kittens fighting for the same warm spot in the sun.

I'd never met a human who made me want to see tomorrow. Until now. That scared me, too. But I didn't care. Because right now, I wanted to see how far this human would go. Just how deep that well ran.

Maybe I'd tell Vali about him. Maybe not.

Maybe I'd keep him for myself a little longer.

At least until Shirone got back from the underworld.

Because I was only curious. Yep. That's the only reason.

SMACK

Poor human or poor tree? Difficult to tell which suffered more damage with that one.