The classroom of 1-A buzzed with morning energy as students filtered in. Yang, still adjusting to navigating in Izuku's shorter frame, strode through the door with confident swagger – a walk completely foreign to Midoriya's usual nervous gait.

"Morning, everyone!" Yang called out cheerfully, throwing herself into Izuku's seat with a relaxed posture that made several classmates do a double-take. She propped one foot on the desk, leaning back casually.

Iida's hand chopped through the air mechanically. "Midoriya! Your foot! That is not proper classroom etiquette!"

"Oh, lighten up!" Yang grinned, but lowered the foot. Her easy smile was so different from Izuku's usual nervous ones that it seemed to transform his face entirely. "Beautiful morning, isn't it?"

Bakugo, who had been watching with narrowed eyes since her entrance, growled from his seat. "What's got you so damn chipper, Deku?"

Yang turned, meeting his glare with an amused smirk. "What, I can't be in a good mood?" She winked. "You should try it sometime, might help with those stress wrinkles you're developing."

The classroom went dead silent. Kaminari's jaw literally dropped.

Bakugo's hands sparked. "The fuck did you just say to me?"

"You heard me, Sparky." Yang stretched, completely unbothered by his growing rage. "Those explosions are pretty cool though. Bet they pack quite a punch!" She made finger guns at him, grinning at her own pun.

"Did... did Midoriya just make a pun?" Kirishima whispered to Sero, who could only shake his head in bewilderment.

Ochako approached Yang's desk, her round face filled with concern. "Are you feeling okay, Deku? You seem... different."

Yang turned, and without thinking, flashed her most winning smile – the one that usually had boys at clubs tripping over themselves. "Aw, worried about me? That's sweet of you!" She reached out and playfully booped Ochako's nose. "But I'm feeling great!"

Ochako's face went from pink to scarlet in record time. She stumbled backward, floating a few inches off the ground in her flustered state.

"Careful there!" Yang caught her hand, steadying her. "Though I guess floating's not really a problem for you, huh? Pretty handy quirk you've got!"

"I... you... Deku..." Ochako sputtered, her blush intensifying at the casual contact.

Bakugo slammed his hands on his desk, small explosions crackling. "Since when do you act like this, you damn nerd?!"

"Since when do you care?" Yang shot back, raising an eyebrow. "Unless... are you jealous of the attention?" She waggled her eyebrows suggestively.

More explosions. "DIE!"

"Mr. Aizawa's coming!" Tsuyu warned from the doorway.

Yang settled back in her seat, but not before throwing one last wink at the fuming Bakugo. She caught sight of All Might merchandise on her desk and quickly tried to recall what little she'd gleaned about this world's top hero from the posters in Izuku's room.

'Right, gotta at least pretend to be a fanboy,' she thought, though the merchandise just reminded her of Port's overenthusiastic lectures.

"Deku?" Ochako had recovered enough to speak, though her face was still pink. "Are you sure everything's alright? You seem so... confident today."

Yang wondered if this Izuku kid was really that much of a nervous wreck normally. "Just trying something new!" She flashed another easy smile. "By the way, that uniform looks really cute on you!"

Steam practically erupted from Ochako's ears as she fled to her seat. Behind her, Mina and Hagakure were furiously whispering and gesturing between Ochako and Yang.

Aizawa slouched in, his capture weapon dragging along the floor. His bloodshot eyes swept the classroom, lingering for a moment on Yang. "Midoriya. You're sitting differently."

"Just working on my posture, sir!" Yang saluted cheekily. Several classmates gasped at her casual tone with the intimidating teacher.

Aizawa stared for a long moment before sighing. "Whatever. Today we're practicing rescue scenarios. Get changed and meet at Ground Beta."

As the class moved to grab their hero costumes, Yang examined the green suit hanging in Izuku's locker. 'Not bad, but it could use some yellow accents...'

"Deku!" Ochako called out, then immediately blushed again when Yang turned. "Um... good luck with training!"

"Thanks, gorgeous!" Yang replied automatically, then realized she probably shouldn't be quite so forward in this body. But Ochako was already floating away again, face burning.

Bakugo shouldered past roughly. "Watch yourself, Deku. Don't know what's got into you today, but you're acting fucking weird."

"Aw, you do care!" Yang clutched her chest dramatically. "I'm touched!"

"DIE!"

As Yang headed to change, she couldn't help but grin. This whole body-swap situation was bizarre, but at least it was entertaining. These kids were wound way too tight – especially that explosive one. A little friendly flirting never hurt anyone!

'Though I probably shouldn't break too many hearts in this kid's body,' she mused, examining Izuku's freckled face in the locker room mirror. 'Wouldn't want him coming back to a bunch of confused admirers... if we ever switch back.'

She flexed experimentally, impressed by the muscle definition. 'Kid's been working out! Not quite my level, but not bad at all. Now, let's see what this "quirk" thing can do...'

The green lightning that crackled around her borrowed form made her grin widen. Maybe this wouldn't be so bad after all.

"Midoriya!" Iida's voice carried through the locker room. "Why are you posing in the mirror? We must not be tardy!"

"Coming, coming!" Yang called back, throwing one last wink at her reflection. "Time to show these kids how to have some fun!"

The scene continues to build through character interactions and reactions, using Yang's natural personality to create humorous situations while establishing the differences between her and Izuku's usual behavior. The physical descriptions help ground the reader in the setting, while the dialogue and reactions reveal character dynamics and personalities.

aaa

Ground Beta's training area stretched out under the afternoon sun, concrete buildings creating an urban maze around the sparring circle where students gathered. Yang stood across from Kirishima, bouncing lightly on the balls of Izuku's feet as she sized up her opponent.

"Remember," Aizawa called from the sidelines, wrapped in his capture weapon like a cocoon, "this is a quirkless combat exercise. Focus on fundamental techniques."

'Perfect,' Yang thought, grinning. 'Hand-to-hand is my specialty.' She settled into her usual fighting stance – or tried to. Izuku's shorter frame and different weight distribution made her usual boxer's pose feel awkward.

"Ready when you are, Midoriya!" Kirishima called, bringing his fists up in a basic guard. "Though you're standing kind of weird..."

Around the circle, their classmates watched with interest. Ochako fidgeted nervously while Bakugo glared with suspicious intensity.

"Begin," Aizawa drawled.

Yang immediately launched forward with what should have been her signature right hook – except Izuku's arm was shorter than she was used to, causing her to miss completely. Kirishima blinked in surprise as she stumbled past him.

"Dude, you never start with wild swings like that!"

Recovering quickly, Yang spun around, trying to compensate for the different body proportions. 'Right, shorter reach, different center of gravity. I can adjust!'

She threw a combination she'd practiced thousands of times: jab, cross, hook. But each punch fell short or went wide as muscle memory betrayed her. Where her body expected to feel the familiar weight of Ember Celica, there was nothing. When she tried to use her semblance to power through a hit, no flames came.

"What's wrong with Deku?" she heard Mina ask from the sidelines. "His form is totally different!"

"Indeed!" Iida agreed. "He appears to have abandoned his usual analytical approach for a more aggressive style!"

Kirishima pressed his advantage, throwing straight punches that Yang would normally dodge easily. But Izuku's body didn't move the way she expected, and a solid hit caught her in the ribs.

'Okay, this isn't working,' Yang thought, frustrated. She tried to activate One For All, forgetting Aizawa's "no quirks" rule, but couldn't quite grasp how Izuku's power worked anyway. The green lightning flickered briefly before fizzling out.

"Midoriya!" Aizawa barked. "What did I say about quirks?"

"Sorry!" Yang called back, ducking under Kirishima's next punch. She tried to counter with an uppercut, but again her muscle memory betrayed her. Where she expected to feel the familiar resistance of her gauntlet's recoil, there was nothing, throwing her timing off completely.

Kirishima capitalized on her awkward positioning, sweeping her legs out from under her. Yang tried to catch herself the way she would in her own body, but Izuku's different proportions sent her sprawling instead.

"Match!" Aizawa called.

"Nice try, Midoriya!" Kirishima offered a hand up, which Yang took with a rueful grin. "But what was with all those wild haymakers? You usually fight way smarter than that!"

"Just... trying something new?" Yang suggested, rubbing Izuku's sore ribs. She was used to taking much harder hits in her own body.

"Well, it certainly was... different," Iida commented, chopping his hands through the air. "Your usual calculated style is much more effective!"

Bakugo stomped forward, red eyes blazing. "The fuck was that, Deku? Since when do you fight like some back-alley brawler?"

"What's wrong, Sparky?" Yang couldn't help needling him despite her loss. "Worried about me changing up my style?"

"You looked like you were trying to fight way bigger than you are," Ojiro observed thoughtfully. "Almost like you're used to having longer reach and more weight behind your punches."

Yang froze. The tailed student had hit uncomfortably close to the truth.

"And what was with that stance?" Mina added. "It looked like a boxer's guard, but like, for someone taller?"

"Perhaps Midoriya has been studying new fighting styles!" Iida suggested. "Though I must advise against abandoning your strengths for untested techniques during evaluated matches!"

Ochako approached, concern written across her face. "Are you okay, Deku? You seem really off today..."

"Just fine!" Yang assured her with another winning smile that made the gravity user blush. "Guess I should stick to what this bo- what I know best!"

"Damn right you should," Bakugo growled. "Whatever this weird shit is you're pulling today, knock it off. It's pissing me off even more than your usual nonsense."

"Aw, you say the sweetest things!" Yang batted Izuku's eyes at him, causing several nearby students to choke back laughter at Bakugo's apoplectic expression.

"Next match," Aizawa interrupted before Bakugo could explode. "Uraraka versus Ashido."

As the girls stepped into the circle, Yang rubbed her borrowed body's arms, feeling the foreign network of scars beneath the PE uniform. 'This kid's been through some serious training... I should probably try to figure out how his body actually fights instead of forcing my style.'

She caught sight of her reflection in a nearby window – green hair, freckles, a face that still felt wrong – and sighed. 'Wonder how he's doing in my body... hope he hasn't tried using my semblance without knowing how. Ruby would never let me live it down if he burned off my hair...'

The Beacon library stretched out in grand splendor, towering bookshelves casting long shadows in the afternoon light filtering through tall windows. At a corner table surrounded by stacks of textbooks, Izuku sat hunched over his notes, long blonde hair tied back in a messy ponytail as he muttered while writing.

"The varying properties of dust crystals seem to follow consistent elemental patterns, though the interaction between types suggests complex chemical reactions that could be categorized by..." He paused his muttering to draw another detailed diagram.

Team RWBY stood several feet away, watching with mounting concern.

"She's been like this for three hours," Ruby whispered, silver eyes wide. "Yang has never voluntarily studied for more than twenty minutes!"

"And look at those notes," Weiss added, peering at the detailed diagrams and chemical formulas sprawling across multiple pages. "They're... actually comprehensive."

Blake's bow twitched as she gripped her book tighter. "This reminds me of a novel I read once... about a shapeshifting Grimm that replaced someone after studying their life..."

"Not helping, Blake!" Ruby hissed.

Izuku looked up from his notes, lilac eyes brightening. "Oh, you're all here! Great! I've organized study guides by subject and created a schedule to ensure optimal coverage of all test topics!" He started shuffling papers enthusiastically. "I've color-coded everything and cross-referenced with previous exam materials..."

The girls exchanged alarmed looks as Izuku continued his excited explanation.

"I've broken down Professor Port's lecture patterns and identified recurring themes that are likely to appear on tests. Did you know he mentions Death Stalkers approximately 3.7 times per class? And Professor Goodwitch's practical exams tend to follow specific combat scenario patterns that we can prepare for by..."

"Okay, who are you and what have you done with my sister?" Ruby demanded, pointing dramatically.

Izuku froze mid-explanation, suddenly very aware of how un-Yang-like he was being. "I... just thought we should be prepared?"

"Yang Xiao Long has never used the phrase 'optimal coverage' in her life," Weiss declared, crossing her arms.

"Or made color-coded study guides," Ruby added.

"Or taken notes that didn't include at least one doodle of herself punching something," Blake observed, eyeing the detailed dust reaction diagrams.

Izuku tried to think of how Yang would handle this situation. "Well... you could say this test is really... firing me up?" He attempted finger guns, but his nervous delivery made it fall flat.

Blake's hand drifted toward Gambol Shroud. "In chapter three of 'The Body Snatcher's Betrayal,' the imposter's first mistake was trying too hard to be studious..."

"I'm not a body snatcher!" Izuku protested, then realized that was exactly what a body snatcher would say. "I mean... I'm just trying to help everyone pass!"

"Yang doesn't help people pass by studying," Ruby said suspiciously. "She helps by giving encouraging thumbs up and saying 'You got this!' while doing none of the work herself."

"Although," Weiss mused, examining Izuku's notes, "these are actually really good. The dust interaction chart is more detailed than anything in our textbook..."

Izuku brightened. "Right? The way different types of dust combine reminds me of how certain qu- I mean, semblances can work together for compound effects! I've theorized several potential combinations that could enhance team combat effectiveness..."

He caught himself as he noticed their stares becoming even more suspicious. "But uh... probably better to just... punch stuff? Yeah! Punch it all! Woo!"

"Now you just sound like you're making fun of Yang," Ruby pouted.

"Chapter seven: 'The imposter grows desperate and begins to overcompensate...'" Blake narrated ominously.

"Could we maybe focus on studying?" Izuku tried desperately, gesturing to his carefully organized notes. "I've prepared practice questions and everything!"

"Practice questions?" all three girls said in unison, horror growing on their faces.

"That's it!" Ruby declared. "We're calling Professor Ozpin! The real Yang would rather fight an army of Ursai than make practice questions!"

As Ruby reached for her scroll, Izuku frantically gathered his notes. "Wait! I can explain! I just... really want us all to do well! As a team! Because... teamwork makes the dream work?"

"Now you're just saying random motivational phrases," Weiss noted critically.

"Chapter twelve: 'The mask begins to crack...'" Blake continued, now actually pulling out Gambol Shroud.

"Would it help if I made a pun?" Izuku offered weakly.

"Try it," Ruby challenged, narrowing her eyes.

"Um... this situation is getting... un-BEAR-able?" Izuku attempted, sweating under their scrutiny.

Weiss pinched the bridge of her nose. "That was physically painful to hear."

"Yang would never make a pun that weak," Ruby agreed. "She has standards! Low ones, but they exist!"

Blake had pulled out her scroll. "Chapter fifteen: 'The final confrontation...'"

"Okay, okay!" Izuku held up his hands in surrender. "Maybe I'm just... trying to be a better student? People can change, right?"

"Yang once set her homework on fire because it was, and I quote, 'looking at her funny,'" Ruby countered.

"To be fair, it was giving her a lot of trouble," Blake admitted, then shook her head. "But that's not the point! Chapter sixteen clearly states—"

"Blake, please stop narrating the body snatcher novel," Weiss interrupted. "Though I admit, the parallels are... concerning."

Izuku looked at his elaborate study materials, then at their suspicious faces, and made a decision. Channeling everything he'd observed about Yang's personality, he stood up, stretched dramatically, and declared, "You know what? You're right! All this studying is making my brain hurt. Who wants to go punch something instead?"

The girls stared at him.

"That... actually sounded almost like Yang," Ruby said uncertainly.

"Still not quite right though," Weiss mused. "The delivery was a bit off."

"Chapter nineteen: 'The creature nearly perfects its mimicry, but—'"

"Blake!"

Izuku gathered his notes, trying to act casual. "Well, if no one wants to study, I'll just... review these myself! In private! Where no one can see me being studious and suspicious!"

He backed away slowly, nearly tripping over his borrowed body's new center of gravity. As he retreated, he heard their continued discussion:

"Should we be worried that Yang's gotten... smart?" "I'm more worried about why she keeps muttering about quantum dust physics..." "Chapter twenty-one—" "Blake, I swear to god..."

Izuku didn't stop moving until he reached Yang's dorm room, slumping against the door with a sigh. 'Note to self: studying is apparently extremely out of character for Yang. Maybe I should try punching more things instead...'

He looked down at his detailed notes and carefully organized study guides, then at a poster of Professor Port flexing on the wall. 'But first, I really should finish analyzing the correlation between his mustache movements and test question topics...'