My Monster Evolution in One Punch Man

Beat it.

Since Rover was being so enthusiastic, Hansen didn't see any reason to play it cool. With a sharp, fluid leap, he launched himself like a lightning bolt, his body a sleek blur in motion, and landed squarely atop the massive beast's broad skull.

Beneath his boots, the texture of Rover's coarse, rugged fur greeted him, dense and tough like braided steel. Beneath that was the searing heat of a body brimming with dormant power, like standing on top of a volcano that hadn't decided whether it wanted to erupt yet. For just a moment, Hansen was overwhelmed with a surge of reckless, almost childish joy.

Who else could understand this feeling?

On just the second day after transmigrating, he was already riding a Dragon-level monster, and not because he'd forced it or tricked it. The thing had offered!

This was the kind of insane treatment that would make even main characters jealous. Of course he was going to ride it. Who wouldn't?!

"Roar!" (Hold on tight!)

Rover had no clue what kind of internal monologue Hansen was having. If it did, it probably would've rolled its eyes, flung him off its head, and blasted him with a real "Scorching Blast" to cool him down.

But instead, the massive dog gave a spirited roar, lowered its stance, and without warning, exploded into motion.

BOOM!

The ground split with the force of its launch as the pitch-black beast surged forward with a velocity completely unthinkable for its size.

In only a few lunges, Rover was already bounding off the tunnel walls, rocketing into the deeper levels of the base like a living missile.

Whoosh!

Air screamed past them. The rock walls on either side turned into streaking smears of color as if the entire world had gone into fast-forward.

Perched on Rover's head, Hansen remained firmly planted, feeling every jolt of impact through his legs, every shockwave vibrating through the beast's skull. The rushing wind buffeted his body, and the sheer speed made his heart race.

This was the raw might of a Dragon-level monster. It wasn't something data could quantify or words could capture. It had to be felt.

Rover's speed was jaw-dropping. Before Hansen had even gotten the chance to enjoy the ride properly, the temperature in the air began to shift. The wind grew cool and moist. Faint echoes started bouncing off the tunnel walls, a signal that the terrain ahead was changing.

Then, in a blink, the tunnel opened up, and they surged into a vast, open underground cavern.

It was like entering a hidden world.

A long, ancient-looking stone bridge stretched across the hollow space, suspended over a bottomless black chasm. The roof of the cavern soared high above, vanishing into shadows. Beneath them, the faint sound of flowing water echoed up from the darkness, a slow, distant current, likely an underground river far wider than anyone aboveground could ever imagine.

But Rover didn't stop because of the view.

As he came to a halt, paws planted firmly on the stone bridge, Hansen's senses sharpened. His eyes narrowed behind the faceplate.

They weren't alone.

Roughly a kilometer ahead, at the far end of the bridge, there was another presence. Strong. Solid. And definitely not friendly.

At the center of the bridge, a green figure blurred in and out of sight, darting between scattered boulders in a blisteringly fast training routine. The sheer speed was astonishing, so fast that the eye could only catch streaks of green afterimages flashing back and forth, accompanied by sharp, slicing noises as the figure tore through the air itself.

He was a striking man, dressed in a tight black combat suit, with flowing, wavy green hair trailing like a whip behind him. For a brief moment, during a pause in his motion, Hansen managed to get a clear look.

Long, narrow eyes, sharp like a hawk's. Fingers tipped with jet-black claws, lethal and curved. Strange black leopard-like markings ran across his face, neck, and arms, standing out vividly against his pale skin. Every line of his body exuded savage tension, like a predator poised to strike. There was nothing subtle about it. The aura he gave off was pure bloodlust, primal, feral, and dangerous.

One glance was enough. This guy wasn't human anymore.

Hansen's gaze sharpened, and a name immediately surfaced in his mind.

He knew who this was.

A notorious S-Class criminal. Speed-o'-Sound Sonic's senior. One of the top assassins trained in the Ninja Village.

Gale Wind.

Hansen had read about him before transmigrating. The man had accepted Monster Cells in pursuit of greater strength and joined the Monster Association after a full transformation. Hansen just hadn't expected to run into him so soon.

Clearly, Psykos had been laying the groundwork far earlier than the timeline suggested, quietly expanding her forces behind the scenes and recruiting elite assassins from the underworld to support her eventual rebellion.

Still, none of this mattered to Rover.

The giant black beast didn't care who was in its path. Still in high spirits, eager for a long-overdue bath, it stomped forward without a shred of hesitation, stepping boldly onto the bridge with earth-shaking force.

At that exact moment, Gale Wind was still immersed in the euphoric rush of speed brought on by his transformation. But his highly tuned ninja senses suddenly went haywire.

A crushing force surged toward him, heavy, overwhelming, like an avalanche roaring down from above or a tidal wave threatening to swallow him whole.

His face paled immediately.

Whoosh!

The green blur came to a halt. His feet skidded against the stone as he snapped his head up, eyes narrowing into dagger-like slits. His pupils shrank to pinpoints the moment he saw the source.

Even after his transformation, with strength approaching the Dragon-level threshold, a cold sweat rolled down the side of his face.

He recognized the monster immediately. Every assassin worth their name knew that monstrous silhouette.

Overgrown Rover.

A core executive of the Monster Association. An apex Dragon-class being.

Gale Wind's body tensed like a coiled spring. His monster-enhanced pride meant nothing now. His assassin's instinct screamed at him to survive.

He didn't dare make a move. Didn't dare raise a hand. Didn't even let a single hostile thought slip through his mind.

He simply stood still, spine rigid and jaw clenched, lowering his head ever so slightly as Rover approached, a silent gesture of submission from one predator to another much, much higher on the food chain.

Afraid that Rover might see him as a potential threat, Gale Wind didn't hesitate. The black stripes covering his body, along with the feral, monstrous features, swiftly receded like a retreating tide. In less than a second, he had reverted from his transformed state back into a completely human appearance. His overwhelming aura instantly dropped from early Dragon-level to high-tier Demon-level.

Careful not to provoke the beast, he took a cautious step forward. His intention was clear: show deference to the terrifying executive monster and avoid unnecessary conflict.

But in the very next second, his pupils contracted, and he froze on the spot.

What did he just witness?

From atop Rover's massive head, a dark, insect-like figure had jumped down effortlessly. That alone would've been bizarre, but what truly made Gale Wind's mind stall was the presence that accompanied the figure.

Demon-level.

No doubt about it, the figure radiated a strong Demon-level aura, and yet... It had just been riding Rover. Calmly. Casually. Like that was completely normal.

What kind of sick joke was this?

A Demon-level monster riding a peak Dragon-level executive? Was the hierarchy of the Monster Association a complete mess? Did someone scramble the power rankings while he wasn't looking?

The scene was so absurd that Gale Wind's finely honed assassin instincts failed to offer any logical response. His thoughts spiraled into a deadlock.

Across from him, Hansen landed cleanly on the stone bridge, his body clad in sleek, black armor that bristled with spiked edges. Every inch of him radiated a sharp, oppressive aura that hinted at something far more dangerous than just brute strength.

In that moment, the system activated, scanning the lifeforms within range and automatically pulling up Gale Wind's profile.

A translucent screen flickered into view in front of Hansen.

…

[Monster: Gale Wind]

[Disaster Level: Demon (High)]

[Ability 1: Swift Wind (SSR)]

After undergoing monsterization, Gale Wind gained command over wind itself, drastically boosting his movement speed and reaction time. He can disappear in a flash, reappear mid-strike, and accelerate in unpredictable bursts beyond the capacity of human reflexes.

[Ability 2: Monsterization (SR)]

A transformation trait triggered by consuming Monster Cells. Particularly effective for those with precise bodily control. Grants the ability to switch between human and monster forms at will, with a substantial increase to all physical attributes in monster form.

[Ability 3: Gale Assassination Technique (SR)]

A personalized assassination method combining secret Ninja Village arts with individual combat mastery. Excels in using wires, short blades, and various stealth weapons for silent takedowns.

[Ability 4: Storm Blade Kick (SR)]

A specialized taijutsu technique passed down in the Ninja Village. A high-velocity spinning kick that generates destructive cutting force. Even a glancing hit can inflict deep wounds.

…

Hansen's eyes scanned the list, but his attention quickly locked onto the first two skills:

"Swift Wind"

"Monsterization"

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