Chapter 1:

EXP Farming in Diapers

I Was Reincarnated as someone who gets stronger after every fight

The streets of Tokyo were bathed in the pale glow of streetlamps when chaos erupted.
Sirens wailed. Officers shouted. The crowd scattered like startled birds.

“Evacuate the area now!” one officer bellowed, his voice sharp with urgency.
“Satoshi, get that man out of here—quick!”

Satoshi sprinted across the pavement, spotting a lone figure strolling casually in the danger zone. “Hey, mister! Wait a second—Yusuke-sensei?! What are you doing out here at this hour?”

Yusuke adjusted the strap of his satchel, looking mildly puzzled. “I just finished my last project and was heading home.”

“Move! There are terrorists in the area!” Satoshi shouted.

The crackle of automatic gunfire split the night. Something heavy dropped from above—a bag landing near them with a dull thud.

Yusuke’s eyes widened. “Damn it! There are still people here!” Without hesitation, he grabbed the bag and clutched it to his chest.

(What am I doing? I have a family at home… and he doesn’t. Why am I throwing myself in the way?) His lips curved into a grim smile. (Maybe… because that’s what anime protagonists do.)

The explosion swallowed him whole.

Somewhere else—warm, muffled, and strange.

(It’s… warm. Is this the afterlife?)

Yusuke’s eyes flickered open—only to be met by an unfamiliar face looming above him.
No… not just unfamiliar. Massive.

A woman’s voice gasped. “Look! He’s opened his eyes!”

A man leaned into view, beaming. “Really?! Congratulations, son! Welcome—”

(Wait… what? Where am I?)

The couple exchanged glances.

“We didn’t even think of a name…” the man mused.

“Yes… how about Yusu—”

“Ryoma,” Yusuke blurted. Except it wasn’t his adult voice—it was… deeper. Much deeper.

Silence. Then—

“Did… did we just give birth to an eighteen-plus child?” the mother whispered in horror.

“His voice is deeper than mine!” the father sputtered.

(Tch. I’ll have to fake it. Act like I’m on autopilot. Hide my memories… for now.) Ryoma forced an awkward, babyish laugh. (Someone save me from this misery.)

“Say ‘Mama,’” the woman cooed.

“Mm ma... mma… mama,” Ryoma offered.

The father’s jaw dropped. “He’s not developing—he’s mutating at will! Say ‘Papa’!”

Ryoma stared at him blankly. (Who makes their newborn say ‘Mama’ and ‘Papa’ right after spawning into this world?)

The father leaned closer, poking his cheek again. Ryoma smirked inwardly. (Oh, I’m absolutely teaching you a lesson.)

Warm liquid sprayed across the man’s clothes.

“AGHH! YOU—! I need to wash this off!” The father stormed off, leaving the mother chuckling softly.

"This is what you deserve after forcing him."

(Mom’s kind… now, where the hell am I?) Thought Ryoma.

“You’re in a different world,” a voice chirped.

Ryoma’s eyes darted around until they landed on… a tiny bird, flapping in through the window.

(Wait… is this… isekai?) He squinted. (Hold on—who the hell are you?)

“Your personal assistant,” the bird replied matter-of-factly. “Call me Arashi.”

(Personal… assistant? Am I suddenly important now?)

“If you don’t like it, I’m leaving!” Arashi turned away with a huff.

(Weird bird.)

“I HEARD THAT!”

(Sorry, sorry!)”

“Hide the fact you remember your past life,” Arashi warned. “If your parents find out, they’ll hand you over to the Holy Cops.”

(Cops? I’m not even six minutes old and you’re telling me I could end up behind bars?)

“Rules are rules.”

(These are terrible rules—)

Ryoma’s mother began humming a lullaby, rocking him gently.

(Who puts their baby to sleep right after they’re randomly spawned into a broken fantasy world?) He sighed inwardly. (Guess I’ll have to play along.) He shut his eyes, feigning sleep.

As soon as she left the room, his eyes snapped open—glowing faint red. He hopped off the bed, landing silently on the floor.

“Will I have to stay this small for years?” he muttered.

“Not necessarily,” Arashi said. “Kill monsters to grow. You already have powers—you just haven’t figured them out yet.”

(Yep. Definitely an isekai. What am I? A protagonist? Or... No no nevermind... I have to get out of this house first, and for that...)

He balled his fist, swung it at the door—thud. Nothing.

Arashi sighed. “Door handle. Sofa. Bat. You know what to do.”

(A ten-minute-old baby is about to do gymnastics… ohhh my god! if Mom or Dad sees me, I’m finished. But still… let’s do this.)

He clambered onto the sofa. From up there, the floor looked like the base of Mount Everest.

“If I die, I’ll change the world anyway. Here I go!”

He leapt, grabbed the bat, and hooked it onto the door handle, twisting it with his weight. The door creaked open.

Beyond it lay green grass, a nearby city—and scorpions the size of small dogs crawling across the yard.

“This,” Arashi said, “is your new world.”

Ryoma squinted. “Yeah, yeah thanks! my eyes were under maintenance.”

Arashi sighed, "Thinking himself as a roaster."

“Start with one of the small scorpions,” Arashi instructed. “Focus on your arms. Crush it.”

Ryoma concentrated for a while, his eyes reddening wildly. Nothing happened.

Arashi pecked him on the forehead.

“OW! OW! OW! Pecking a fifteen-minute-old baby is a crime!”

“Stop forcing it. Feel your hand,” Arashi insisted.

Ryoma inhaled deeply… focused… and—

PFFFT!

"Ahh!" Ryoma's face reddened relaxingly.

“Did you just—?!” Arashi sputtered.

“NOT MY FAULT!”

The nearest scorpion turned toward them, scuttling fast. Ryoma focused, and this time, a burst of energy surged from his palms. The creature lifted into the air—then, with a clench of his fist, it crumpled like paper.

“I… I did it!”

His body floated a few centimeters off the ground—then stretched, his frame growing until he looked about four years old.

“Whoa! Four years old in seventeen minutes!”

“I’ve been fighting for four years… and it felt like minutes.”

“IT WAS ONLY 20 MINUTES DUMBASS!" Sighed Arashi, "That’s the trick. But now the growth rate slows.”

“Oh I understand… so it’s like EXP in a video game? Classic isekai nonsense.”

Ryoma opened his palm. His fingers twitched, stiff and sharp like spikes.
"The hell? My hand feels like it could punch through steel."

“You nicked that from the big one’s stinger. Iron Nail. Not bad,” Arashi said, tilting his head.

“Oh great, I’m basically a walking toolbox now. What next? chainsaw knuckles?”

Before Arashi could answer, a voice cut through the trees.

“Ryoma! Where are you?!”

His mother stepped into the clearing.