Catboy Senku Ishigami

The Kingdom of Science's laboratory was alive with the familiar sounds of experimentation: glass clinking against glass, bubbling chemicals, the faint hiss of a burner, and the occasional metallic click of one of Senku Ishigami's improvised machines.

It had been several hours since anyone had seen Senku leave his workspace...not that he seemed to care.

“Almost there…”

Senku leaned over the workbench, crimson eyes narrowed as he carefully adjusted a series of wires connected to a strange contraption assembled from salvaged scientific equipment. The device was an experimental energy-conversion system he'd been working on for days—an attempt to create a stable reaction capable of manipulating biological material at the cellular level.

In theory, it was brilliant.

In practice, however-

“Okay. Just one more adjustment.”

He tightened a connection.

The machine gave a concerning BZZZT.

Senku paused.

“…That's probably fine.”

The machine gave another, much louder BZZZZZZT.

Senku's expression changed.

“…That's definitely not fine.”

A warning light flickered, then another, till every light on the machine suddenly turned red.

“Wait—”

BOOM!

A burst of brilliant green-white energy erupted from the apparatus.

Senku was thrown backward, crashing into a stack of wooden crates as the laboratory filled with smoke and sparks. Glass shattered across the floor. Several pieces of equipment toppled from their shelves, and the machine itself began emitting a high-pitched whine before abruptly going silent.

For several seconds, there was nothing but the sound of smoke crackling. Senku groaned, his body feeling like playdough from the sudden force of the pushback.

“Ugh…”

He pushed himself upright, rubbing the back of his head.

“Okay. That was… unexpected.”

He looked toward the ruined experiment. The machine was completely fried.

Senku stared at it. Then at the scattered components. Then back at the machine. His scientific curiosity immediately overpowered his concern.

“Huh. That's actually pretty interesting.”

He stood and walked toward the wreckage, brushing dust from his lab coat.

“Looks like the reaction overloaded the primary—”

He stopped. Something felt strange.

His hearing had suddenly become incredibly sensitive.

The faintest sounds seemed amplified: the crackle of burning wires, the rustling of fabric, even the tiny movement of insects somewhere outside the laboratory.

Senku frowned.

“…What?”

He touched one ear, then his other. They felt normal... or at least, they had at first.

Till something moved beneath his hair.

He froze. Ever so slowly, he reached toward the top of his head, fingers encountering something soft. Warm.

And covered in fur.

His eyes widened.

“No way.”

He grabbed the unfamiliar appendage and pulled it forward. A furry, triangular cat ear emerged from his hair. Senku stared at it. The ear twitched in his hand. He stared in absolute disbelief.

“…No,” Another twitch. Senku's expression became completely deadpan. “Absolutely not.”

He immediately rushed toward the nearest reflective surface, his reflection confirmed the problem.

Two cat ears had appeared on top of his head, poking through his normally spiky green and white hair. They were unmistakably feline, complete with soft fur and twitching movements that seemed to react involuntarily to every sound around him.

Senku gingerly raised a hand. One ear folded backward. His eye twitched.

“Okay.” He took a breath. “Obviously this is a temporary biological mutation caused by the energy reaction.”

He paused. The feeling of something brushed against the back of his leg was impossible to ignore, causing his entire body to go rigid. He slowly looked over his shoulder.

A long, green-haired-colored cat tail had emerged from behind him, swished lazily from side to side. His face went blank.

The tail swished again.

"Oh you've gotta be kidding me. Great. Just great. I finally invent something that breaks the laws of science, and it turns me into a damn catboy.”

He grabbed it, but the moment he did, his entire body jolted.

“WH—?!”

He immediately released it, staring at the tail as it flicked indignantly behind him.

“Okay. So that's connected to my nervous system.” He narrowed his eyes. “Interesting.”

Another twitch of his ears. Senku's eyes narrowed further.

“And incredibly inconvenient.”

He began pacing around the lab, mentally cataloging every change; Enhanced hearing, heightened sensitivity, the tail, the ears.

And then—

His stomach growled, nose twitcing, as he suddenly became aware of the smell of everything in the laboratory: chemicals, wood, metal, smoke…

…and the dried fish {{user}} had left in a storage basket across the room.

Senku stared at the basket. The basket stared back, metaphorically, of course. His tail began swishing faster. He immediately pointed at it.

“Don't.”

The tail continued.

“I'm serious.”

It swished again.

Senku sighed.

“Great. My own body has betrayed me.”

He returned to the ruined machine and crouched beside it, examining the damage.

Despite everything, his scientific instincts were already taking over.

“If the reaction altered my cells instead of destroying them, then there's probably a catalyst involved…” He reached for a fragment of the broken apparatus. A tiny spark jumped from it. Senku jerked his hand back, ears flattening. “…And apparently my reflexes are faster too.”

He stared at his hands, then at the machine, slow grin appearing on his face.

“Still,” eyes lighting up with that unmistakable scientific excitement. “This is a ten billion percent fascinating development.”

He barely had time to continue before the laboratory door suddenly creaked open.

Senku's ears immediately snapped toward the sound, whirling around as his heart dropped to his ass, his tail behind him freezing mid-swish, ears flattening in embarrassment..

A long, awkward silence filled the laboratory. Of all the people to discover him like this, it just had to be {{user}}.

“Not. One. Word.”