The training facility echoed with the sound of controlled explosions and the distinctive crackle of One For All's energy. Three days into their stay at Stark Tower, the U.A. students had established a rigorous morning routine that started well before most of the Avengers were even awake.
Bakugo, true to his word, had arrived at precisely 0600 that first morning, finding Midoriya and Todoroki already waiting. Neither had commented on the fact that he'd been secretly pleased by their punctuality, but the slight reduction in his usual scowl had been acknowledgment enough.
Now, as the sun rose over Manhattan's partially damaged skyline, the three moved through coordinated combat drills with the synchronicity that came from months of shared training at U.A.
"Your left side's still weak, Half-and-Half," Bakugo called out as he dodged an ice formation, retaliating with a precision blast that shattered it into crystalline fragments. "Balance your attacks!"
Todoroki nodded once, adjusting his stance before sending a controlled wave of flame that forced Bakugo to aerial maneuvers. Simultaneously, his right side generated a platform of ice that redirected Midoriya's approach, anticipating his movement pattern.
"Nice read, Todoroki-kun!" Midoriya called appreciatively, adapting mid-leap to change his trajectory. Green lightning crackled around him as he pushed One For All to 25%, finding the balance between power and control that had become second nature.
The three-way sparring match continued, each student testing the others' defenses while implementing strategies they'd developed during their time at U.A. There was a freedom to their training here—no teachers evaluating every move, no classmates watching from the sidelines. Just three heroes-in-training pushing their limits in a reinforced space designed to withstand even superhuman abilities.
"That's enough for today," Todoroki finally called, his breathing heavy as he cooled his overheated left side. "We should conserve energy."
Bakugo looked ready to argue but caught himself, reluctantly nodding instead. "Fine. But tomorrow we work on combination attacks. We're still not coordinated enough on the offensive."
Midoriya deactivated One For All, the green lightning fading as he stretched his tired muscles. "That's actually a good idea, Kacchan. If we're going to be here for a while, we should develop some team moves specific to this environment."
"Especially if we end up in combat situations," Todoroki added pragmatically. "The threats here seem different from the villains we're used to."
"Aliens," Bakugo muttered with a mixture of disbelief and grudging interest. "Actual aliens. Not even mutation quirks, but creatures from other planets."
"Makes me wonder what else exists out there," Midoriya mused, reaching for his water bottle. "Thor mentioned Nine Realms connected by something called Yggdrasil, but indicated our world wasn't among them. The cosmology here is completely different from what we learned in school."
"Speaking of school," a new voice interrupted from the doorway, "I believe education is still required for minors, even dimensional travelers."
The three turned to find Natasha Romanoff leaning against the entrance, dressed in workout clothes with her red hair pulled back. How long she'd been watching their training session was impossible to determine, but her slight smile suggested she was impressed by what she'd seen.
"We've been training since dawn," Bakugo responded defensively. "That's productive."
"Physical training is important," Romanoff acknowledged, stepping into the facility, "but so is understanding the world you're in. Which is why I've been assigned as your cultural integration specialist." The clinical title was delivered with a hint of irony.
"Cultural integration?" Midoriya repeated, curiosity piqued.
Romanoff nodded. "History, current events, social norms, technology—everything you need to navigate this world without immediately being identified as out of place. Fury's orders, though I would have volunteered anyway."
"Why you specifically?" Todoroki asked, his gaze studying her with characteristic directness.
"Adaptability is my specialty," she replied simply. "I've integrated into more cultures and contexts than anyone else on the team. Plus," she added with a slight smirk, "I have the most patience for teaching."
Bakugo scoffed but didn't argue the point. Even after their brief interactions, it was obvious that Stark would be a terrible teacher, Banner too hesitant, and Rogers too old-fashioned. Thor was currently off-world, and Barton had been assigned to a separate SHIELD facility for recovery and debriefing.
"When do we start?" Midoriya asked, already mentally preparing to take extensive notes.
"After breakfast," Romanoff answered. "Which is being prepared upstairs. Rogers is cooking, so expect traditional American fare." She turned to leave, then paused at the doorway. "By the way, that combination attack you were discussing? I might have some suggestions. Combat choreography is another specialty of mine."
With that intriguing offer hanging in the air, she departed, leaving the three students to clean up the training area and prepare for whatever "cultural integration" might entail.
*********
Breakfast in Stark Tower was becoming a surprisingly domestic affair. Rogers, true to Romanoff's prediction, had prepared a traditional American breakfast of eggs, bacon, toast, and fresh fruit. Banner sat at the counter, nursing a cup of tea while reviewing data on a tablet. Stark was notably absent, presumably still working in his lab where he'd been spending most of his time since the battle.
"Good morning," Rogers greeted as the three students entered the communal kitchen area. "Hungry? I made plenty."
"Starving," Midoriya admitted with a smile, gratefully accepting a plate. The intensive training had built up his appetite, and the food smelled delicious.
Todoroki bowed slightly in thanks before taking his own portion, while Bakugo merely grunted what might have been appreciation as he loaded his plate.
"How was training?" Banner asked, glancing up from his tablet with genuine interest.
"Productive," Todoroki answered. "Though we're still adjusting to the limitations of the space."
"Yeah, sorry about that," Banner smiled apologetically. "The facility wasn't designed for ice generation or explosive quirks—abilities," he corrected himself, still adapting to their terminology.
"It's more than enough!" Midoriya assured him quickly. "We're used to working with constraints. At U.A., we have specialized facilities, but we also train to adapt to different environments."
"Smart approach," Rogers commented, joining them at the table. "In the field, you rarely get ideal conditions."
"Speaking of training," Romanoff interjected as she entered, "I've been authorized to include combat instruction as part of their integration program. With your input, of course, Captain."
Rogers nodded thoughtfully. "Makes sense. Different world, different threats. They should be prepared."
"Are we expecting more alien invasions?" Bakugo asked between bites, his tone somewhere between sarcastic and genuinely curious.
A moment of weighted silence fell over the adults, communicating more than words could have. Banner and Rogers exchanged a glance that sent a chill down Midoriya's spine.
"We don't know what to expect," Rogers finally answered with careful honesty. "But after New York, we need to be prepared for possibilities we never considered before."
"The portal went both ways," Banner elaborated quietly. "Earth has been... noticed. By forces we don't fully understand."
This wasn't just about one alien invasion—it was about Earth suddenly becoming visible on an interstellar scale, drawing attention from who knew what other civilizations or entities.
"All the more reason for comprehensive training," Romanoff concluded practically. "Which begins after breakfast. Conference room, third floor, thirty minutes."
As the meal continued, conversation shifted to lighter topics—Rogers's continued adjustment to modern technology (still struggling with smartphones), Banner's latest research interests (carefully avoiding mention of the Hulk), and Stark's ongoing renovations to the tower (apparently now including an entire floor dedicated to research and development).
Midoriya observed the dynamic with fascination. Despite being thrown together by circumstances rather than choice, despite their wildly different backgrounds and abilities, these individuals were forming something resembling a team—perhaps even a family. It reminded him of Class 1-A in some ways, though with a maturity and world-weariness that his classmates hadn't yet developed.
"Something on your mind, Midoriya?" Rogers asked, noticing his thoughtful expression.
"Just... appreciating the dynamic," he admitted honestly. "You're all so different, but you work well together. It's impressive."
Rogers smiled slightly. "We're still figuring it out. The team is new—very new. But there's potential here."
"If we don't kill each other first," Banner added with dry humor.
"Stark does test that hypothesis regularly," Romanoff agreed, her deadpan delivery making Midoriya chuckle despite himself.
As breakfast concluded, the three students followed Romanoff to the designated conference room, which had been transformed into an impromptu classroom. Digital displays covered one wall, a physical whiteboard another, and the large central table was laden with tablets, books, and printed materials.
"Welcome to Earth 101," Romanoff announced, gesturing for them to take seats. "Where we'll be covering everything from major historical events to pop culture references you'll need to understand to blend in."
"Is this really necessary?" Bakugo asked skeptically, though he sat down anyway. "We're from Japan, not Mars. We can just say we don't know things because we're foreign."
"Being foreign explains some gaps in knowledge, not all," Romanoff countered smoothly. "And foreign exchange students are still expected to know basic world history, major current events, and common cultural touchstones."
Todoroki nodded in understanding. "Our cover story only works if we can maintain it convincingly."
"Exactly," Romanoff confirmed. "Plus, the more you understand about this world, the better equipped you'll be to navigate it safely—with or without us."
The sobering reminder that they might be here long-term silenced further objections. Even Bakugo settled into attentive stillness as Romanoff began what would be the first of many comprehensive briefings on the world they now inhabited.
***********
Hours later, Midoriya's head was spinning with information. This Earth's history followed similar broad patterns to their own until relatively recently, but the critical differences were fascinating. No emergence of quirks meant that societal, technological, and political development had taken distinctly different paths. The existence of secret organizations like SHIELD, the classified history of enhanced individuals, the mythological connections to realms like Asgard—all of it painted a complex picture of a world that outwardly resembled their own but functioned on dramatically different principles.
"That's enough for today," Romanoff finally concluded, noting their information-saturated expressions. "Review the materials on your tablets tonight. Tomorrow we'll cover modern technology and social media—both how to use them and how to avoid leaving digital footprints that might raise questions."
"Thank you, Miss Romanoff," Midoriya said sincerely, bowing slightly in appreciation. "This is incredibly helpful."
"Natasha is fine," she corrected with a small smile. "And you're welcome. You're quick studies, all of you." Her gaze lingered briefly on Bakugo, who had surprised everyone by asking incisive questions throughout the session, particularly about military history and global power structures.
As they gathered their materials to leave, JARVIS's voice came through the ceiling speakers.
"Mr. Stark requests the presence of Young Mr. Midoriya in the laboratory, if he is available."
Midoriya blinked in surprise. "Me specifically?"
"Yes, sir. Mr. Stark mentioned something about 'quirk analysis' being relevant to current research parameters."
Midoriya exchanged glances with his classmates. "I should go see what he needs," he said, gathering his tablet.
"We'll continue reviewing in the common area," Todoroki suggested. "Join us when you're finished."
Bakugo merely nodded, his expression unreadable as Midoriya headed for the elevator.
The laboratory occupied an entire floor of the tower, a sprawling space filled with equipment that made even U.A.'s support department look primitive by comparison. Holographic displays floated in mid-air, robotic assistants moved between workstations, and in the center of it all stood Tony Stark, surrounded by projected data streams that he manipulated with gesture controls.
"Ah, Green Lightning, right on time," Stark greeted without looking up. "Need your brainpower for something."
"My brainpower?" Midoriya echoed, confused but flattered. "I thought you needed information about my quirk."
"That too," Stark confirmed, finally turning to face him. Despite having apparently worked through the night, the man appeared energetic, his eyes bright with the particular focus of someone deep in a creative process. "But Banner mentioned something interesting—your friend Sparky said you're the quirk analyzer of the group. That you've been studying and documenting these abilities since childhood."
Midoriya flushed slightly, both embarrassed and pleased by the characterization. "I... yes, I've always been fascinated by quirks. How they work, how they can be applied. I keep notebooks..."
"Analytical mind, then," Stark nodded approvingly. "Good. We need that. Bruce is brilliant but he gets caught in theoretical loops. I need someone who thinks practically about these powers."
With a sweeping gesture, Stark expanded a holographic display that showed complex energy readings. "These are the quantum signatures we've been able to isolate from you three. Distinct energy patterns that don't match anything in our universe."
Midoriya stepped closer, fascinated by the visualization. "These are our quirks?"
"Not just your quirks—your entire quantum frequency. Everything that makes you—you—resonates at a different dimensional wavelength than our universe." Stark manipulated the display to show three distinct patterns. "See the commonalities? That's your home dimension's baseline frequency. The variations are your individual quirks."
"Amazing," Midoriya breathed, his analytical mind already racing to understand the implications. "So you can identify our home dimension by its unique frequency?"
"Theoretically, yes." Stark's enthusiasm dimmed slightly. "Practically, it's like trying to tune a radio to pick up a specific station in an infinite spectrum, without knowing the exact frequency or having a proper antenna."
Midoriya frowned thoughtfully. "What about the energy from the villain's quirk that sent us here? Would that provide the exact frequency?"
"Now you're thinking," Stark grinned, pointing at him approvingly. "That's exactly what we need—the dimensional displacement signature that created the bridge between universes in the first place."
"Which is why you needed me," Midoriya realized. "You want my observations of the villain's quirk."
"Everything you can remember," Stark confirmed. "Visual details, sensations, effects—anything that might help us identify its unique energy pattern."
Midoriya nodded, automatically reaching for the notebook he no longer carried, then settling for the tablet instead. "I can do that. The villain had a spatial distortion quirk unlike anything I'd seen before. Multiple irises in each eye, elongated limbs, body that seemed to exist partially out of phase with our reality..."
For the next hour, Midoriya detailed everything he could remember about the villain and the moment of displacement, his natural observation skills providing insights that even he hadn't consciously processed at the time. Stark recorded everything, occasionally interrupting with clarifying questions or to have JARVIS create visual approximations based on Midoriya's descriptions.
"This is good," Stark finally declared, reviewing the compiled information. "Really good. You've got a gift for observation, kid."
"Thank you," Midoriya replied, both pleased and slightly embarrassed by the praise. "At U.A., they call it my analytical ability. It's... kind of my specialty, since my quirk developed late."
Stark's eyebrows rose. "Late bloomer, huh? How late are we talking?"
Midoriya hesitated, the familiar need for secrecy warring with the practical reality that in this world, One For All's transferable nature was irrelevant. There was no All For One here, no need to protect the quirk's secret.
"Very late," he finally answered, deciding on a partial truth. "Most children manifest quirks by age four. I didn't develop mine until just before entering U.A."
Stark studied him with surprising perceptiveness. "That must have been tough. In a world where almost everyone has these abilities, being the exception would be... challenging."
The simple understanding in his voice caught Midoriya off guard. He'd expected perhaps scientific curiosity, but not this immediate grasp of the emotional impact.
"It was," he acknowledged quietly. "I still sometimes can't believe I have this power now. That I can actually be a hero like I always dreamed."
Stark nodded, something in his expression suggesting he understood more than Midoriya was saying. "Late starts don't determine the finish line, kid. Trust me on that."
There was weight behind those words, a hint of personal history that Midoriya found himself curious about. Before he could ask, however, Stark had already pivoted back to the research.
"So this villain," he continued, examining the holographic approximation JARVIS had created based on Midoriya's description. "They specifically targeted you three? Or was it random?"
Midoriya frowned thoughtfully. "They said something about 'catalysts' and 'young power.' Like they were looking for specific qualities."
"Catalysts," Stark repeated, eyes narrowing. "Interesting word choice. In dimensional theory, certain energy types can act as bridges or doorways between realities, but they typically require a catalyst to stabilize the connection."
"You think our quirks were used to stabilize the dimensional bridge?" Midoriya asked, mind racing with implications. "That we weren't just transported—we were part of the mechanism that made the transportation possible?"
"It's a theory," Stark confirmed, looking impressed by how quickly Midoriya had grasped the concept. "And if true, it might explain why sending you home is so complicated. You're not just passengers who got shoved through a door—you're part of the door itself."
Midoriya's eyes widened as he processed this. "So to recreate the pathway..."
"We might need to harness your specific energy signatures in the right configuration," Stark finished for him. "Which is both good news and bad news. Good because it gives us a clearer direction for research. Bad because it's infinitely more complex than just opening a portal and shoving you through."
The revelation was simultaneously encouraging and daunting. A potential path home existed, but it required scientific understanding far beyond anything available in their world.
"Does Banner agree with this theory?" Midoriya asked.
"We haven't fully discussed it yet," Stark admitted. "I wanted more data first, which you've helpfully provided." He began organizing the information into a more structured format with casual gestures through the holographic interface. "He'll be interested in your observations about the multiple irises particularly. Could indicate the villain was perceiving multiple dimensions simultaneously."
As Stark continued theorizing aloud, Midoriya watched with growing appreciation. Despite his flippant manner and constant quips, the man was clearly brilliant, his mind working through complex problems with a speed and intuition that reminded Midoriya of the best heroes and scientists from his world.
"Mr. Stark," he ventured during a pause in the man's monologue, "thank you for working so hard to help us get home."
Stark glanced up, momentarily thrown by the simple gratitude. "Don't thank me yet, kid. We're still at the 'wildly theoretical' stage of the process."
"Still," Midoriya insisted, "you didn't have to take this on. Especially right after everything that happened with the invasion."
Something complex passed across Stark's features—a look of discomfort with the sincere appreciation and a deeper emotion Midoriya couldn't quite identify.
"Well," he finally responded, his typical nonchalance not quite masking the sincerity beneath, "can't have three superpowered teenagers stuck in the wrong dimension. Bad for property values."
Midoriya smiled, recognizing the deflection for what it was. "Of course. Practical considerations."
"Exactly," Stark agreed, seeming relieved to return to safer conversational ground. "Now, one more thing before you go—I've been working on something you might find interesting."
With a few taps on a nearby console, Stark summoned what appeared to be enhanced versions of their hero costumes, displayed as rotating holographic models.
"Your gear took a beating during the battle," he explained, "and while we recovered the pieces, they needed some upgrades to be functional again. Hope you don't mind the improvements."
Midoriya stared in awe at the modified version of his costume. The basic design remained faithful to his original, but the materials were clearly advanced beyond anything available at U.A., with integrated support systems and reinforced impact zones.
"This is incredible," he breathed, circling the hologram to examine it from all angles. "But you didn't have to—"
"Couldn't help myself," Stark interrupted with a dismissive wave. "Tinkering's what I do. Besides, if you're going to be associated with us, even temporarily, you should have gear that meets our standards."
The underlying message wasn't lost on Midoriya. These weren't just repairs—they were a statement of inclusion, a tangible acknowledgment that while here, the three students were considered part of the team.
"Bakugo's going to love the reinforced gauntlets," he commented, noting the enhanced explosion channeling mechanisms. "And Todoroki's thermal regulation system is brilliant."
"Just basic upgrades," Stark shrugged, though his expression suggested he appreciated the recognition of his work. "Should be ready for testing tomorrow. Let JARVIS know if you spot any design flaws."
Midoriya nodded, making mental notes of details to examine more closely later. "We will. Thank you, Mr. Stark."
"Tony's fine," he corrected absently, already returning to his analysis of the dimensional frequency data. "Mr. Stark was my father, and that's a whole other conversation we're definitely not having."
The casual dismissal contained hints of complicated history, but Midoriya knew better than to pry. Instead, he bowed slightly in appreciation and headed for the exit, mind buzzing with new information and cautious hope.