What if Boros survived(OPM)

Hero Association Headquarters

"We're detecting unusually high tectonic activity underneath City Z."

"What?!"

"That's impossible! Geographically, such activity shouldn't occur in that area," said the executive chief, his tone incredulous.

"We suspect it's monster-related, sir," an officer replied. "City Z has been abandoned for a while, but we've seen several monsters entering and leaving the zone where the activity is concentrated."

Another officer interjected. "Wait, sir, we have a report of King entering a neighboring city not too long ago. He might be close enough to detect the tremors and investigate."

The chief paused, considering the information. "Call every available S-Class hero immediately and have them report here."

One of the officers hesitated. "But sir, if King is already there—"

"He might need backup," the chief interrupted. "Besides, we can't be sure he'll act on it. Do as I said—call every available S-Class hero!"

.................

Underground – Monster Association

Boros stood amidst the rubble, looking up at the hole in the cavern ceiling he had created.

"I've killed a leader," he mused, "but that doesn't mean my fun has to end."

He smirked. "There are still plenty of monsters left up there. Maybe if they all attack me at once, I might have to exert myself a little."

Boros powered down, deciding to conserve energy and make the upcoming battle more challenging. He crouched, then launched himself upward with tremendous force.

The alien smashed through the layers of rock and emerged in the Monster Association's main chamber.

Gyoro Gyoro stared in shock. "You... you're alive!"

"What happened down there? Where's Orochi?"

Boros met her gaze calmly. "I killed him. The battle was enjoyable, but it didn't give me what I wanted." He cracked his knuckles. "Now it's your turn. Try to make this exciting for me."

Before Gyoro Gyoro could react, Boros dashed forward. She attempted to activate her psychic powers, but she was blown to bits before she could utter a word.

The remaining monsters froze in disbelief. Some turned to flee, while others gathered their courage and leapt down to face the intruder. Among them were Black S and Overgrown Rover.

Suddenly, the ground beneath Boros quaked as two massive claws burst through the floor.

"Huh, what's this?" Boros muttered, leaping to avoid the attack.

But the maneuver proved to be a mistake. Elder Centipede erupted from the ground, slamming into Boros mid-air and driving him into the cavern ceiling. The colossal insect kept pushing, forcing Boros through the layers of rock until they burst onto the surface of the abandoned City Z.

Boros rolled off the centipede and landed on the street. Dust and rubble rained down around him as Elder Centipede emerged from the hole.

More monsters followed through the newly formed tunnel—Black S, Homeless Emperor, Fuhrer Ugly, Gums, Overgrown Rover, Pureblood, and several lower-level creatures like Rhino Wrestler.

Goketsu, watching from the shadows, decided against joining the fray. He respected Orochi's power, having experienced it firsthand. If Boros had defeated even Orochi, then fighting him would be pointless. Goketsu quietly retreated into one of the tunnels.

...............…

The Battle Above Ground

Black S began multiplying rapidly, while Homeless Emperor and Overgrown Rover fired a barrage of energy blasts at Boros.

The alien shrugged off the explosions, unimpressed. "Orochi's attacks were far stronger. If even he couldn't harm me, what chance do you fools have?"

Boros charged at Rover, unleashing a series of devastating punches. The massive hound howled in pain as Boros finished the combo with a powerful kick, sending Rover crashing through several buildings.

Homeless Emperor, stunned at first, began charging an enormous energy sphere. Boros noticed and smirked. "Let's see if this one tickles a little," he muttered, deciding to let Homeless Emperor prepare his attack.

In the meantime, he turned his attention to Fuhrer Ugly and Gums. As he approached, Black S multiplied further, creating a tsunami of clones that blocked Boros' path.

"I see," Boros said, observing the clones. "A multiplication ability. Interesting."

"It's not just multiplication," replied Black S. "I can increase my numbers to several trillion. Think you can take down that many?"

Boros chuckled. "Numbers don't matter. A weakling is still a weakling."

The alien lunged into the swarm, every punch generating shockwaves that disintegrated dozens—if not hundreds—of Black S clones at a time. But no matter how many he destroyed, the clones kept multiplying.

Soon, a tidal wave of Black S crashed down on Boros. The alien smiled, releasing a surge of energy that obliterated thousands of clones in an instant.

Despite this, the tide regenerated quickly, washing over Boros once again.

"Still think you can win?" taunted Black S. "I am countless. You can't destroy me, no matter how hard you try!"

Boros grinned. "True, but the more you multiply, the weaker each clone becomes. You'll never be able to hurt me. I could keep going for weeks."

The alien's confidence only grew as he prepared for the next wave of attacks.

Boros continued battling the endless tide of Black S clones while the other monsters prepared their attacks. The alien's energy showed no signs of waning as he plowed through his opponents with relentless force.

Above ground, the tremors grew stronger, and the skies darkened ominously.

Deep underground, Saitama and Genos entered the sewer tunnels, their curiosity piqued by the strange activity.

"Something big is going on down here," Genos said.

Saitama yawned. "I hope it's worth my time."