As the echoes of his "Lit Fuse" attack faded across the now-turbulent waters of Lake Sciliora, Katsuki hovered, panting, his mind still racing despite the physical exertion. The satisfaction of his new underwater capabilities and the nascent "Cluster Style" was immense, but his brain, always a relentless engine of combat innovation, was already leaping to the next possibility.
Deku. All Might. Their "Smashes."
The thought, as always when it concerned his childhood rival and the former Number One Hero, was accompanied by a familiar cocktail of resentment, rivalry, and a grudging, deeply buried acknowledgment of their sheer, overwhelming power. He'd seen Deku's Full Cowling Smashes, seen All Might's legendary United States of Smash. They weren't just punches; they were focal points of incredible, body-encompassing force, capable of changing weather patterns and leveling city blocks.
His own explosions, while devastating, had always been more… directed. Localized to his palms, or now, his feet. Even his Howitzer Impact, while wide-area, was a spinning concentration of multiple blasts. He'd never truly tried to channel his entire explosive potential, both Quirk and magic, into a single, overwhelming concussive punch.
"A Smash, huh?" he mused aloud, his voice a low growl that barely carried over the hissing steam rising from the lake. "That damn nerd and All Might… always with the over-the-top, showy bullshit." But even as he sneered, a spark of intense curiosity, of competitive fire, ignited within him. Could he do something like that? Not a copy, never a copy. But his own version. An explosion so massive, so all-encompassing, it would make even their Smashes look like firecrackers.
He understood the principle, intuitively. It wasn't just about arm strength. It was about channeling energy from the legs, through the core, into the shoulders, and finally, into the fist, a kinetic chain reaction. With his Quirk, it would involve a massive, simultaneous ignition of nitroglycerin sweat across his entire body, focused into one point. With his 'Explode' magic, it would be a colossal gathering and compression of magical energy, drawn from every fiber of his being and unleashed in a singular, cataclysmic burst. Or, even better, both. A perfect, devastating synergy.
The name came to him then, unbidden, stark and terrible in its implications, a name that resonated with the sheer, world-altering potential he was contemplating.
"Explode: Oppenheimer Smash!"
The words felt heavy, dangerous, even to him. But the allure of such ultimate destructive power was too strong to resist. He had to try it. Just once. To see.
He descended slowly, landing on the most stable, widest rock ledge he could find, bracing himself. This wasn't an attack he could unleash carelessly in mid-air; the recoil alone might be catastrophic. He took a deep, shuddering breath, feeling the familiar tingle of his Quirk activating across his skin, the sweat glands working overtime. Simultaneously, he reached deep within himself, drawing upon his 'Explode' magic, pulling in vast quantities of the azure energy, compressing it, supercharging it.
His entire body began to glow, a furious, incandescent orange-red from his Quirk, overlaid and intermingled with the intense, vibrating blue of his magic. The air around him crackled and warped, pebbles at his feet beginning to levitate and smoke. The combined energy felt… immense. Almost too much to contain. His muscles screamed in protest, his bones felt like they were vibrating apart. This was power on a scale he had never dared to wield before.
He drew his right arm back, his fist clenched so tight his knuckles were white. He focused all of it – every iota of his Quirk's explosive sweat, every searing particle of his 'Explode' magic, every ounce of his physical strength, every drop of his indomitable will – into that single point.
For a heartbeat, all was still. Then, with a roar that was less human and more the sound of a star collapsing, he punched.
He didn't aim at the lake, or the forest, or anything specific. He aimed at the empty space before him, at reality itself.
The world erupted.
It wasn't just an explosion; it was a miniature apocalypse. A blinding, hemispherical dome of pure, white-hot energy expanded outwards from his fist with impossible speed, vaporizing everything in its path. The initial shockwave was a physical wall, flattening trees for hundreds of yards around the lake's edge as if they were blades of grass. The surface of Lake Sciliora seemed to boil away, vast quantities of water instantly turning to superheated steam, creating a colossal, mushrooming cloud that billowed thousands of feet into the night sky. The ground beneath Katsuki's feet fractured and buckled, the rock ledge he stood on disintegrating into a shower of molten slag. The sound was beyond deafening; it was a pressure wave that resonated deep in the chest, a sound that felt like the tearing of the very fabric of existence.
The light was so intense, so all-consuming, that for a terrifying moment, Katsuki himself was lost within its glare, a silhouette against a man-made sun.
When the primary blast subsided, the aftermath was… breathtaking in its devastation. A vast, circular area around where Katsuki had stood was simply gone, scoured clean down to bedrock, which glowed an angry red. The edge of Lake Sciliora had been violently reshaped, its waters still churning and steaming, a new, deep crater blasted into its basin. The forest for a huge radius was a mangled ruin of snapped trunks and burning embers. The colossal steam cloud still dominated the sky, slowly beginning to dissipate, but leaving behind an eerie, orange glow that illuminated the widespread destruction.
Katsuki was still standing, somehow. He was on his hands and knees, gasping, his entire body trembling uncontrollably. His new clothes, despite their enchantments, were shredded, hanging off him in smoking tatters. His skin was raw, scorched, every muscle screaming in agony. Blood trickled from his nose and ears. The power he had unleashed had taken a tremendous toll, pushing him far beyond his limits.
But a wild, almost insane grin was plastered across his face. His crimson eyes, reflecting the fires he had created, blazed with a terrifying triumph.
"Ho… ly… shit…" he wheezed, each word a painful effort. He'd done it. He'd actually fucking done it. An attack of such monumental, world-breaking power… it was exhilarating and terrifying in equal measure.
He knew, with a certainty that chilled him even amidst the inferno he'd created, that this "Oppenheimer Smash" was not a technique to be used lightly. It was a weapon of last resort, an ultimate expression of destructive force that could very well kill him if he wasn't careful. The name itself was a grim reminder of the potential consequences.
But he had it. Another terrifying tool in his arsenal. Another step towards becoming undeniably, overwhelmingly Number One, in this world or any other. He had touched the sun, and he had not been entirely consumed.
On the far side of the lake, hidden deep within the now-burning remnants of the forest, Team Natsu had been thrown to the ground by the sheer force of the shockwave. They were dazed, deafened, their ears ringing, their eyes still recovering from the blinding flash.
Natsu, covered in soot and leaves, pushed himself up, staring with wide, disbelieving eyes at the mushroom cloud still dominating the sky. "What… what IN THE ACTUAL HELL WAS THAT?!"
Lucy, her hair singed, her clothes torn, could only whimper, clutching Plue (who had somehow, miraculously, remained in her arms) for dear life. Gray was speechless, his usual cool demeanor shattered, his jaw hanging open as he surveyed the apocalyptic landscape. Erza, though visibly shaken, her armor dented and scratched, was already scanning the epicenter of the blast, her expression a mixture of profound shock and grim assessment.
"That… that wasn't just an explosion," she managed, her voice hoarse. "That was… that was a cataclysm." She looked at her stunned teammates. "Master Makarov wanted us to be a safety net. I don't think there's a net in the world strong enough to catch that."
Happy and Carla, who had been knocked out of the sky, were slowly picking themselves up, their fur ruffled, their eyes wide with terror. "He… he blew up the lake!" Happy stammered. "He blew up the forest! He almost blew up the sky!"
The sheer scale of destruction was beyond anything they had ever witnessed from a single individual, even amongst the S-Class mages of Fairy Tail, even compared to the destructive rampages of dark guilds or rampaging Etherion blasts. Katsuki Bakugo was not just powerful. He was, potentially, one of the most destructive forces this world had ever seen. And he was utterly, terrifyingly alone in his power. The playful idea of "connecting" with him now seemed like a distant, naive dream. How did one connect with a walking, talking apocalypse?
---
The triumphant, almost manic grin on Katsuki's face slowly faded as the adrenaline began to recede, replaced by an all-consuming wave of agony. Every nerve ending in his body screamed. His vision swam, blurring the edges of the hellscape he had created. He tried to push himself up, to stand, but his limbs refused to obey, trembling violently, devoid of strength. He collapsed back onto the scorched, glowing rock, his breath coming in ragged, painful gasps.
"Fuck…" he choked out, a bloody froth bubbling at his lips. "My body… is hurt… Bad." He coughed, a wracking, body-shaking spasm that sent fresh waves of torment through his battered frame. He could feel broken bones, torn muscles, internal injuries he couldn't even begin to diagnose. The recoil from the Oppenheimer Smash had been far more devastating than he'd anticipated. It wasn't just physical exhaustion; it was systemic damage, his very cells protesting the outrageous energies he'd forced them to channel.
A grim, horrifying thought pierced through the haze of pain. "So this is what Deku felt." He remembered the aftermath of Deku's early, uncontrolled uses of One For All – the shattered limbs, the agonizing recoveries. He'd always sneered at the nerd's weakness, his inability to handle the power he'd been gifted. Now, lying broken and bleeding in a crater of his own making, Katsuki tasted a bitter, unwelcome dose of that same agonizing reality. The irony was not lost on him, even through the pain.
He lay there, helpless, vulnerable, a state he despised more than anything in the world. The fires he had ignited around the lakeshore cast flickering, demonic shadows over his prone form. He could hear the crackle of flames, the hiss of steam, the distant groan of tortured earth. He was alone, critically injured, in an alien world. For a terrifying moment, a flicker of genuine fear, cold and sharp, pierced through his bravado.
Across the ravaged lake, Team Natsu, having somewhat recovered their senses, stared at the distant, unmoving figure of Katsuki amidst the devastation. The initial shock was slowly giving way to a dawning horror at the extent of his injuries, clearly visible even from this distance by the unnatural stillness of his form.
"He's not moving!" Lucy cried out, her voice strained with panic, pointing a trembling finger. "Natsu, he's really hurt!"
Natsu, his earlier awe forgotten, was already clenching his fists, his expression a mixture of concern and frustration. "Damn it! What was he thinking, unleashing an attack like that?! Idiot!" Despite his harsh words, his protective instincts, always strong for anyone he even vaguely considered an ally, were kicking in.
Erza's face was grim. "That level of power output… the physical toll must be immense. He could be dying." She made a swift decision. "Carla!" she called out, her voice sharp and commanding. The white Exceed, still looking shaken, immediately flew to her side. "Fly back to Magnolia. Get Wendy. And if you can find her, if she's willing, bring Porlyusica. Tell them it's critical. A powerful mage has sustained life-threatening injuries from his own magic. Go! Now!"
Carla, recognizing the urgency in Erza's tone, nodded sharply. "Understood, Erza-san!" With a powerful beat of her wings, she shot into the sky, a small white streak heading east with desperate speed.
With Carla gone, Erza turned to the others. "Natsu, Gray, Lucy, Happy. We need to get to him. Carefully. The area is unstable, and he's… volatile, even injured."
They began to make their way around the devastated lakeshore, their progress slow and cautious. The ground was treacherous, littered with debris, smoking craters, and fallen, burning trees. The heat was still intense in places. As they drew closer, the sheer scale of Katsuki's self-inflicted damage became terrifyingly apparent.
They found him lying in the epicenter of the blast, his body a broken mess, his custom-made clothes reduced to scorched rags. He was conscious, barely, his crimson eyes glazed with pain but still holding a spark of defiant fury.
Natsu was the first to reach his side, skidding to a halt, his usual bravado replaced by a shocked concern. "Bakugo! You… you damn idiot! What were you trying to do? Kill yourself?!"
Katsuki coughed again, a wet, rattling sound. He tried to glare at Natsu, but the effort was too much. "Shut… up… Flame-brain…" he rasped, his voice barely a whisper.
Lucy knelt beside him, her face pale with worry. "Oh, gods, Bakugo-san, you're… you're really…" She couldn't bring herself to say the word 'dying.' "Don't try to talk. Help is coming."
Gray stood over him, his expression unusually serious. "That attack… what the hell was that? I've never seen anything like it. It was like you dropped a damn nuke."
Katsuki managed a faint, bloody smirk. "'Oppenheimer… Smash'…" he wheezed. The name itself seemed to cause the others to flinch.
"Oppenheimer?" Lucy whispered, a look of confusion and dawning horror on her face. The name meant nothing to them in terms of historical context, but the sheer destructive intent it carried was palpable.
"Why?" Erza asked, her voice softer than usual, her gaze searching Katsuki's pain-filled eyes. "Why would you unleash something so devastating, knowing the risk?"
Katsuki's gaze flickered towards her, a complex mixture of defiance, pain, and something unreadable swirling in their depths. He didn't answer, just coughed again, a shudder wracking his frame. He didn't have the strength to explain, and even if he did, he wouldn't. He wouldn't admit to the desperate need to feel powerful, to obliterate his own weakness, to silence the ghosts of a world he'd lost.
They barraged him with more questions, a torrent of concern, disbelief, and demands for explanation. Why push himself so hard? What was he trying to prove? Didn't he understand how dangerous that was? Their voices, usually so distinct, blended into a confusing, overwhelming cacophony around him. He closed his eyes, wishing they would all just shut up, wishing the pain would stop, wishing… he didn't know what he was wishing for anymore. He just knew he was broken, and for the first time since arriving in this damn world, Katsuki Bakugo felt utterly, terrifyingly helpless. And he hated it more than the pain itself.