Monday was normal. Tuesday was bargain day at the supermarket. Saitama liked Tuesday.
He didn't get to the supermarket.
He was currently standing on the carcass of a creature that looked like a Godzilla knockoff wearing neon samurai armor. It had been screaming something about "reclaiming the surface world" thirty seconds ago.
Now it was raining chunks of monster meat.
Saitama lowered his fist. Steam curled off the red glove.
"One punch," he muttered, scratching his bald head. His cape fluttered in the shockwave's aftermath. "Again. I didn't even get my heart rate up."
"Sensei!"
Genos landed with a mechanical thud, incinerator cannons cooling down. The cyborg scanned the debris field, his cybernetic eyes whirring and clicking as they processed data.
"That strike," Genos said, pulling out a notepad. "The velocity was suboptimal, yet the impact force exceeded the theoretical limit of atomic bonding. If I calculate the wind resistance against your bald—"
"Genos."
"Yes, Sensei?"
"Did you get the cabbage?"
Genos froze. "I... was analyzing the threat level, Sensei."
Saitama's face went blank. The doodle-face. The eyes that looked like two dots drawn with a dying sharpie.
"The sale," Saitama said flatly. "Ended at noon."
"My apologies! I will eliminate the grocery store manager to force an extension!"
"Don't do that." Saitama sighed. The emptiness in his chest wasn't from the lack of a battle. It was from the lack of discounted vegetables. "Let's just go home."
He turned to walk away.
The world crunched.
It wasn't a sound. It was a feeling—like biting into a stale chip, but the chip was the fabric of space-time.
Saitama stopped. He looked back at the spot where the monster had exploded.
The air was cracking.
Not metaphorically. Literal, spiderweb fractures appeared in the empty space, glowing with a sickening, violet light. It looked like someone had taken a baseball bat to the sky.
"Sensei," Genos said, his voice dropping an octave. "My sensors are registering... nothing. No radiation. No heat. Just an absence of data."
"Is it a monster?"
"It appears to be a hole in reality."
Saitama tilted his head. "Can I punch it?"
"I would strongly advise against punching the fabric of exis—"
Saitama punched it.
He didn't hit it hard. Just a love tap. A "wake up" knock.
The crack didn't break. It hiccuped.
For a second, the violet light vanished. Through the hole, Saitama saw something that definitely wasn't Z-City.
He saw a forest. A weirdly vibrant forest. And a kid screaming his lungs out while swinging a giant, dirty slab of iron.
"AAAAAAAAAGH! NOT YET! I'M NOT DONE YET!"
Saitama blinked. "Noisy neighbor."
Then the crack expanded.
It didn't just grow. It tore open like a zipper caught in a shredder. The gravity in Z-City inverted instantly. Cars floated up. The rubble from the samurai-Godzilla drifted toward the violet abyss.
"Sensei!" Genos engaged his thrusters, anchoring himself to the pavement. "The gravitational pull is approaching singularity levels!"
Saitama just dug his heels in. "Annoying."
The hole widened. It wasn't just pulling matter in.
It was pulling them in.
Location: The Clover Kingdom
Magic Knights Headquarters - Training Grounds
"NOT YET!"
Asta's voice could shatter glass. It probably had shattered glass in the Black Bulls base at least once this week.
He swung the Demon-Slayer sword. Heavy. Gritty. The anti-magic poured off him like black smoke, thick and angry.
Fifty thousand swings. That was the goal.
"Oi, shrimp," Yami Sukehiro exhaled a cloud of smoke from the sideline. The Captain of the Black Bulls looked bored, which usually meant he was five seconds away from trying to kill Asta for 'training.' "You're yelling loud enough to wake up the Wizard King. Pipe down."
"I CAN'T PIPE DOWN, CAPTAIN YAMI!" Asta grinned, sweat pouring down his face. His muscles felt like they were packed with burning coals. It felt great. "MY MAGIC IS NEVER GIVING UP!"
"That's not magic, idiot. That's just being stubborn." Yami put a hand on his katana. "Ki check. Something's coming."
Asta stopped mid-swing.
He closed his eyes. He focused. Ki sensing.
He felt the birds. He felt the wind rustling the trees. He felt Magna trying to steal food from Charmy in the kitchen two hundred yards away.
And then he felt... static.
It wasn't Ki. It wasn't Mana. It felt cold. Empty. Like the sensation of a limb falling asleep, but applied to the entire atmosphere.
"Captain..." Asta's eyes snapped open. "Above us!"
The sky over the Clover Kingdom tore open.
Unlike the rifts Asta was used to—spacial magic or portal spells—this was jagged. Violent. Violet lightning arched down, striking the anti-magic training dummies and vaporizing them instantly.
"Spatial magic?" Asta gripped his sword. "No... I can't feel any mana from it!"
"Because there isn't any," Yami muttered. His cigarette fell from his mouth. The Captain looked genuinely rattled. "That's not from here. It's sucking the mana out of the air."
The rift pulsed. A massive suction force hit the training grounds.
Grass, dirt, and dumbbells were ripped upward.
Asta dug the Demon-Slayer sword into the ground. "Hold on!"
"My ride's here, apparently." Yami grabbed a tree root, his dark magic coating his body. "Don't let go, kid!"
"I WON'T!" Asta screamed, his feet lifting off the ground. He hung sideways, anchored only by the sword stabbed into the bedrock. "WHAT IS THIS?!"
Through the rift above, Asta saw something insane.
A city. A massive, grey city made of metal and concrete. And floating in the middle of the hole was a bald guy with a cape, looking confused.
"IS THAT A MONK?!" Asta yelled.
Then the ground gave way. The sword ripped free.
"DAMMIT!"
Asta tumbled upward, falling into the sky, swallowed by the purple static.
Location: Alternated Tokyo, Shibuya
Time: 20:15
It was raining in Shibuya.
Ryomen Sukuna sat on a throne of skulls inside his Domain, leaning his chin on his palm.
Boredom.
Agonizing, tedious boredom.
The brat, Yuji Itadori, was suppressing him well today. Sukuna could feel the boy's emotions—fear, determination, the usual heroic garbage. They were fighting a curse user in a subway tunnel. Low grade. Boring.
"Expanding his cursed energy poorly," Sukuna critiqued to no one. "Sloppy footwork."
Suddenly, the connection severed.
Not the soul connection. The sensory input. The world outside Yuji's body just... stopped.
The water in Sukuna's Malevolent Shrine ceased rippling. The air turned stagnant.
Sukuna sat up. One of his four eyes narrowed.
"Oho?"
The walls of his innate domain—usually an abstract mental landscape—started to vibrate. The ribs of the giant skeleton shrine cracked.
It wasn't Yuji. The brat wasn't strong enough to threaten the internal domain.
This was external pressure.
In the real world, Yuji Itadori skidded to a halt in the subway tunnel. The curse he was fighting—a weird floating eyeball thing—had stopped moving.
"Fushiguro!" Yuji shouted. "Did you see that?"
Megumi Fushiguro summoned his Divine Dog, eyes scanning the dark tunnel. "The shadows... they're acting weird."
They weren't acting weird. They were bubbling.
Every shadow in the tunnel began to boil like tar.
"Nobara, get back!" Megumi shouted, tackling Kugisaki as a pool of black sludge erupted from the floor.
But it wasn't a curse. It was a gateway.
From the darkness, a blue prompt window—like a video game HUD—appeared in front of Yuji's face.
[SYSTEM ERROR]
[DIMENSIONAL BOUNDARIES COMPROMISED]
[INITIATING EMERGENCY MERGE]
"A game window?" Yuji blinked. "Is this your technique?"
"Not mine!" the enemy curse user screamed, before being sucked casually into the floor.
"It's pulling us in!" Kugisaki hammered a nail into a concrete pillar, her hammer glowing with cursed energy. "Hold on!"
"It's no use," a deep voice echoed in Yuji's head. Sukuna.
Sukuna?
"This isn't Cursed Energy, brat," the King of Curses sounded almost... delighted. "Space is collapsing. Might as well jump. Better than being crushed by physics."
"I'm not jumping into a shadow pit!"
"Then fall," Sukuna laughed.
Gravity shifted 90 degrees. The floor became the wall. The tunnel exit became the sky.
Yuji Itadori fell into the darkness, dragging Megumi and Nobara with him.
Location: The Mansion
Status: Maximum Comfiness
"It's cold," Kazuma Satou complained. He pulled the blanket tighter around his shoulders. "Aqua, heat the tea."
"I'm a goddess of water, not a microwave!" Aqua whined, sprawled on the couch with an empty wine bottle balancing on her forehead. "Ask the Explosion Maniac."
"My name is Megumin! And my magic is for destroying castles and demon generals, not reheating beverages!" The crimson demon girl polished her staff lovingly.
"Then Darkness can do it." Kazuma motioned to the blonde crusader standing by the window.
Darkness blushed, her breathing getting heavy. "Use my body as a heat shield? Force me to endure the scalding temperatures to serve my master? Oh, the humiliation..."
"Forget I asked." Kazuma slumped back.
Life was good. They had money. No quests. No Dullahans. Just a lazy Tuesday afternoon in a fantasy world. He had his tracksuit, his kotatsu, and barely any impending doom.
Finally, Kazuma thought. I have achieved true peace.
CRACK.
The roof disappeared.
No explosion. No debris falling down. The roof just ceased to exist.
One second: wooden beams and thatch.
Next second: swirling purple vortex of doom.
Sunlight replaced by a kaleidoscope of colors that hurt to look at.
Kazuma stared up. He didn't scream. He didn't panic. He just felt a profound sense of 'I knew it.'
"Aqua," Kazuma said quietly.
"It wasn't me!" the Goddess wailed, clutching her bottle. "I didn't touch anything! I swear!"
"Darkness," Kazuma tried. "Did you wish for a meteor or something?"
"This pressure..." Darkness was trembling, but not with fear. She had that look in her eyes. The 'this is going to hurt' look. "It feels incredibly heavy! Like the weight of a thousand worlds pushing down on me!"
"Don't enjoy it!" Kazuma snapped.
The wind picked up. Furniture started sliding. The kotatsu—Kazuma's holy sanctuary—lifted off the floor.
"MY TABLE!" Kazuma lunged.
He grabbed the table leg. Aqua grabbed Kazuma's leg. Megumin grabbed Aqua's sash. Darkness grabbed Megumin's cape.
A Daisy Chain of useless idiots.
"KAZUMAAAAA!" Aqua shrieked, tears already defying gravity and flowing up her face.
"Stop screaming! It's annoying!" Kazuma yelled back, activating his Skill. Steal!
He intended to steal a secure anchor point or something to hold onto.
Instead, a small, metallic, rectangular object appeared in his hand.
He looked at it. It wasn't from this world.
It was smooth. Glass screen. Apple logo on the back.
"An iPhone?" Kazuma's eyes widened. "Where the hell did I steal an iPhone from?!"
He didn't have time to check the texts. The vortex roared, and the mansion's living room floor gave out.
The Konosuba party ascended into the chaos, arguing the entire way up.
Location: Infinite Forest, Dimension ???
Tanjiro Kamado smelled blood.
It wasn't fresh blood. It was old. Ancient. But beneath that, he smelled... steel? And sulfur. And ramen broth?
He stopped running. His haori, checkered black and green, fluttered in the sudden gust of wind.
"Nezuko," he whispered, tapping the wooden box on his back. "Stay quiet."
Something was wrong with the forest. The trees here were warped. One tree looked like a normal pine. The one next to it looked like it was made of purple crystal. The one next to that looked like a streetlight bent into a pretzel.
"Zenitsu? Inosuke?" Tanjiro called out.
No answer.
He had been on a mission near Mount Natagumo. Then the fog rolled in—thick, unnatural fog. When it cleared, he was... here.
Where is here?
He sniffed the air again.
Fear. Sharp, acidic fear. Someone was terrified nearby.
Determination. Burning hot. Like charcoal.
Boredom? Someone smelled incredibly, overwhelmingly bored. It was such a confusing scent to pick up in a place that felt so dangerous.
CRASH.
Something fell from the sky about fifty meters ahead.
Tanjiro gripped the hilt of his Nichirin blade. He took a breath. Water Breathing... Tenth Form: Constant Flux.
He moved. Low to the ground, fluid, efficient. He slid behind a cluster of those weird purple crystals.
In the clearing ahead, the dust was settling.
A boy—muscular, loud, wearing a Black Bulls robe—was pulling his head out of the dirt.
"OW! MY HEAD IS HARDER THAN THE GROUND, BUT IT STILL HURTS!"
The boy stood up. He was holding a sword as big as he was. No magic. Tanjiro's nose twitched. No scent of demons. No scent of magic. Just... noise.
Then, a second impact.
Thud.
This one was graceful. A man with strange clothes—tight blue suit, weird boots—landed in a crouch. He had hair that defied gravity, black and spiky.
The spiky-haired man stood up and looked around. He tapped an device on his ear.
"Bulma? Can you hear me?" The man asked. "Interference is bad. I can't sense anyone's Ki. It's all jumbled."
The man looked at the loud boy.
"Yo," the man said, raising a hand. "You see a giant green lizard anywhere? Or a bald guy?"
The loud boy pointed his giant sword at the spiky-haired man. "ARE YOU AN ENEMY? MY MAGIC IS NEVER GIVING UP!"
"Magic?" The man scratched his head. "I'm Goku. You guys seem pretty weak. Are you lost?"
Weak? Tanjiro tensed. The scent coming off this 'Goku' person was... terrifying. It wasn't malicious. It was just vast. Like standing next to the sun. If he wanted to, this man could burn the world.
"WHO ARE YOU CALLING WEAK?!" The boy, Asta, bristled.
Before they could fight, a third noise.
Splaaaat.
A pile of three people dropped from the sky, landing in a heap of limbs and cloth.
"Ow! Get your staff out of my kidney!"
"Kazuma! My holy water spilled!"
"This pain... crashing onto the unforgiving earth... exquisite."
Tanjiro blinked. Chaotic scents. Chaos. Chaos. And... perversion?
He decided to step out.
"Excuse me!" Tanjiro announced, his voice projecting clearly. He bowed slightly, keeping his hand on his sword. "Please, let's not fight! We don't know where we are!"
Goku looked at him. Asta looked at him. The heap of people (Kazuma was currently trying to shove Aqua off his face) looked at him.
"A samurai?" Kazuma muttered, eyes narrowing. "Great. An isekai protagonist with a katana. I bet he has a cheat skill. I bet he's popular with girls."
"I'm Tanjiro Kamado!" Tanjiro said earnestly. "I can smell that everyone is confused. Does anyone know how we got here?"
Goku laughed, putting his hands on his hips. "Nope! But you guys look fun. Wanna spar?"
"Read the room, Muscle-Head!" Kazuma yelled, dusting off his tracksuit. "We just fell through the sky into a dimension that looks like a Picasso painting threw up! We shouldn't be fighting; we should be finding a safe zone and crying!"
Asta lowered his sword. "I can't sense any Ki, but..." He looked up.
Everyone followed his gaze.
The sky wasn't blue. It wasn't night.
The sky was a shattered mirror. In each shard of the sky, a different world was visible.
Tanjiro saw a modern city burning.
Goku saw a green planet exploding.
Kazuma saw a giant castle floating in the clouds.
And descending slowly from the fractured sky was a single figure.
He didn't fall. He walked on the air. He wore a black uniform with red accents, and his eyes—deep red with cross-shaped pupils—glowed with amusement.
"Well, well," a voice echoed, not in their ears, but in their minds. "I expected chaos. But this is a rather interesting tea party."
Anos Voldigoad. The Demon King of Tyranny.
Goku's expression sharpened. "Okay. That guy is strong."
"Strong?" Asta grinned, a vein popping in his forehead. "Good! Maybe he knows the way back!"
"Wait!" Tanjiro shouted, the scent of immense power flooding his nose, overwhelming him. It smelled like death and arrogance that had lasted two thousand years. "Don't provoke him!"
"Provoke?" Anos landed softly, ten feet away from the group. He looked at them like a human looks at ants—not with hate, but with curiosity. "Did you think your fear was enough to stop me from introducing myself?"
"I'm not scared!" Asta lunged. "I'M ASTA!"
Anos simply blinked.
Asta was pinned to the ground instantly. No spell. No movement. Just the sheer pressure of the Demon King's presence pushing gravity down.
"Heavy!" Asta wheezed, struggling to push up.
"Fascinating," Anos mused. "You have no magic power, yet you resist. A bug that lifts weights?"
"HEY!" Asta yelled into the dirt.
"Let him go."
Goku disappeared.
He reappeared in front of Anos, fist cocked. No Super Saiyan. Just base form.
Goku punched. Anos caught the fist with his index finger.
The shockwave flattened the purple crystal trees for three miles.
Kazuma shrieked and hid behind Tanjiro. Tanjiro braced his legs, nearly blown away by the wind alone.
"Not bad," Anos said, smiling. He didn't move an inch. "You might be fit to shine my shoes."
Goku grinned, the excitement of battle flaring in his eyes. "You're tough. I'm getting excited!"
SCREEECH.
A high-pitched mechanical whine cut through the tension. A swirling portal opened up—green and acidic—right between Goku and Anos.
A sleek, bald head poked out.
"Excuse me," Saitama said, holding a grocery bag that had somehow survived the dimensional transit. "Does anyone know where the sales aisle is? This looks like the produce section, but the vegetables are weird."
Silence.
Goku blinked. "Huh?"
Anos looked slightly annoyed at the interruption.
Asta was still yelling at the ground.
Kazuma peeked out from behind Tanjiro. "Oh great. Another weirdo. Is that... a salaryman in a costume?"
Tanjiro sniffed the air again. He focused on the bald man.
He smelled... nothing.
Absolute emptiness.
Like a hole in the world shaped like a person.
"Mister," Tanjiro warned, his voice shaking. "Please be careful. These people are dangerous."
Saitama looked at Anos. He looked at Goku. He looked at the crumbling reality around them.
"I just want to go home," Saitama said deadpan. "My cactus needs watering."
And then the ground beneath them, unable to handle the weight of so many protagonists standing in one postcode, finally gave up.
The shard of reality shattered completely.
They all fell. Together. Into the white void below.
The Crossover had begun.