The air in the courtyard was crisp, the afternoon sun casting long shadows across the training grounds behind the Occult Research Club's building.
I stood opposite Issei, my stance relaxed, yet my mind sharp. Despite his perverted nature, the guy had potential. He was the protagonist of this world, after all. Given time, he would grow into a powerhouse capable of shaking the foundations of Heaven and Hell alike.
But right now?
He was still just a rookie with a sacred gear that had yet to awaken its true potential.
"Alright, Kiba, go easy on me, okay?" Issei said, raising his fists in what I could only assume was his best attempt at a boxing stance.
I smirked. "I'll try."
Around us, the rest of the club had gathered to watch. Rias and Akeno stood near the club's veranda, Rias observing with interest while Akeno sipped her tea, an amused smile on her lips. Koneko sat nearby, nibbling on a snack, though her golden eyes were locked onto the fight.
"Ready?" Rias asked.
I gave a short nod.
Issei clenched his fists. "Let's do this!"
[Combat Detected. Mutations Accelerating…]
I barely had time to process the system's alert before Issei charged. He wasn't fast—at least, not by my standards. His footwork was clumsy, his movements filled with hesitation. A wild swing came at me, telegraphed and sloppy.
I stepped to the side effortlessly, feeling something shift within me as I moved.
[Mutation Progress: 35%]
Interesting. It wasn't just my abilities that mutated—the more I engaged in combat, the faster the changes occurred.
Issei threw another punch, trying to catch me off guard. I leaned back, avoiding it by a hair's breadth, then spun behind him, tapping his shoulder lightly.
"Too slow."
"Damn it!" Issei groaned, stumbling forward.
From the sidelines, Koneko let out a small 'hmph.' "You're weak."
Issei gritted his teeth. "Gimme a break, Koneko-chan! I'm still learning!"
Rias chuckled softly. "You're improving, Issei. But Yuuto's speed is on another level."
I barely heard them. My focus was elsewhere—on the subtle changes I was beginning to feel in my body. My muscles felt lighter, more refined, as if something inside me was breaking past its natural limits.
[Knight's Speed Mutation: 50%]
I decided to push it further.
"Let's try something new," I said, stepping back. "Come at me again."
Issei wiped sweat from his brow. "Alright, here goes nothing!"
He charged, this time putting more force into his step. A reckless lunge, but at least he was trying.
I stepped forward—and suddenly, the world blurred.
A rush of energy shot through my legs, and before I even realized what had happened, I was behind him.
Issei blinked. "Huh?"
Then he collapsed face-first onto the ground, rolling into the dirt.
A silence settled over the training field.
Koneko's cookie stopped halfway to her mouth. Akeno's ever-present smirk widened in amusement. Even Rias raised an eyebrow in surprise.
Issei groaned, sitting up and rubbing his face. "What the hell just happened…?"
I stared at my hands, feeling the residual power fading.
And then—
[Mutation Complete.]
Knight's Speed → Phantom Stride
New Effect: Instantaneously move short distances faster than the eye can follow. Can be chained into consecutive movements.
A grin crept onto my face.
Oh, this was going to be fun.
"That was impressive," Rias commented as I approached the group. "Your speed was already formidable, but now it's on an entirely different level."
I bowed my head slightly. "Thank you, Buchou."
Akeno tilted her head. "That movement just now… it wasn't just speed. It was something more."
She was right. I had felt it, too. Unlike before, where Kiba's Knight's Speed simply enhanced his natural mobility, Phantom Stride allowed me to vanish and reappear in an instant. If used correctly, it would be devastating in combat.
Issei huffed. "Man, you're a monster."
"You'll catch up," I reassured him, clapping his shoulder. "With time."
He groaned. "Yeah, yeah… But seriously, what's your secret? Did you unlock some hidden Knight ability or something?"
I hesitated.
I couldn't exactly tell him, Oh, I have a mutation system that upgrades my abilities beyond their normal limits.
"I guess I just had a breakthrough," I lied smoothly.
Rias narrowed her eyes slightly, but she didn't press further. "Regardless, your progress is remarkable."
Akeno giggled. "Yes, I quite like this new version of Kiba~"
I rolled my eyes but didn't comment. If anything, this was just the beginning.
If my abilities kept mutating, then there was no telling how strong I could become.
And I planned to find out.
Later that night, I sat in my room, deep in thought.
The day's events replayed in my mind—the sparring match, my sudden burst of speed, and the way my body felt different afterward.
I pulled up my system screen.
[Current Abilities:]
1. Sword Birth (Mutating: 45%)
2. Phantom Stride (Complete)
My eyes lingered on Sword Birth. Unlike my speed ability, it was taking longer to mutate. Was it because I hadn't used it in actual combat yet? If so, that meant I needed a real fight to trigger the next stage.
And in this world, I wouldn't have to wait long.
A knock on my door pulled me from my thoughts.
"Come in."
The door opened, and Rias stepped inside, her crimson hair illuminated by the hallway light. She closed the door behind her and folded her arms, gazing at me with quiet intensity.
I straightened. "Buchou?"
"I wanted to talk to you."
There was something in her tone—curiosity, but also caution.
"You've been acting a little… different lately," she said. "Your skills, your reactions—it's like you're improving at an unnatural rate."
I kept my expression neutral. "Is that a bad thing?"
"No," she admitted. "But I want to know… why now?"
She was sharp. As expected of the Gremory heir.
I needed to tread carefully.
"I suppose," I said slowly, "after everything we've been through, I realized I can't afford to stay stagnant. If we're going to face stronger enemies in the future, I need to be prepared."
It wasn't entirely a lie.
Rias studied me for a moment before smiling softly. "I see. If that's the case, then I won't question it further."
She turned to leave but paused at the doorway. "Just don't push yourself too hard, Yuuto."
And then she was gone.
I let out a slow breath.
That had been close.
As I lay back on my bed, I couldn't shake the feeling that things were going to escalate soon.
With my abilities evolving, the battles ahead would be unlike anything in the original timeline. Stronger enemies, greater dangers… but also greater opportunities.
And if the mutation system was truly limitless—
Then there was no telling just how powerful I could become.
A small grin tugged at my lips.
This world belonged to Issei Hyoudou, the Red Dragon Emperor.
But I was no longer just a side character in his story.
I was Kiba Yuuto.
And I'm going to forge my own legend.