Disclaimer: I don't own Fire Emblem Three Houses, all rights to the owners.

Those of you familiar with Byleth: Peculiar Professor and Get to Class, or Else will find this a bit different. Namely, I'm using Female Byleth this time, and I'm giving her a different personality. She's socially incompetant still, but in a different way. Consider this a parallel universe to the other stories. I hope you all enjoy.

Also, did you know Petra is the youngest of all the Black Eagles at 15? Yeah, Petra. Bernadetta, the shortest, is only the fourth youngest at 17. Also, Edelgard is actually the second shortest Black Eagle at 158cm (only above Bernadetta's 150cm). I know it's not really important, I just find it so fascinating to actually have biological information about the characters. For example, I never realized Hubert is both the tallest and oldest of the Eagles. I figured that would have gone to Ferdinand (who, mind you, is the second oldest and third tallest).

Anyways, enough getting sidetracked. Here we go. For some reason I just find Bernadetta the perfect character to test out a quirk for Byleth, so we'll start with her. I guess traumatizing Bernadetta is a right of passage… even if Byleth doesn't directly appear in the first segment at all.

The lavender-haired girl pants and leans against the wall. She casts a furtive look behind her, searching for her pursuer.

"Just a little further Bernie! You'll be safe in your room." She tells herself, half in a panic. "They won't kill you there! It would be too suspicious!"

Bernadetta doesn't actually know who's following her. She saw a figure out of the corner of her eye when she was returning from painting the sunset. Her art supplies are currently stowed in her pockets, and the canvas is under her arm.

"Why me though!? I'm not important!" The girl thinks as she resumes her trip, now walking sneakily because she's still exhausted, back to her room. "M-Maybe they're a vampire, and they want to drink my blood! Or a serial killer who stabs anyone for the fun of it!"

She hears the snap of a twig and her pace picks up. Adrenaline is making up for the energy she would otherwise lack.

"O-Or maybe I made an enemy! Maybe someone hates my art, o-or maybe I damaged something when I went to the greenhouse, o-o-or maybe C-Casper is angry about that time I punched him in the face. Oh gods, it's probably that. It's Caspar!"

That punch was part of a sparring match, and the face is a perfectly valid target because they were both wearing helmets. That bit of rationality doesn't occur to the girl at this moment though. In fact, rationality just isn't her strong suit in general.

"M-Maybe it's Hubert! I knew he was mad about me dropping my quill too close to him! O-Or maybe it's Petra! I-I probably did something horribly offensive to her culture! Oh gods, oh gods…" Bernadetta panics. "Oh gods, what if it's all of them!? What if they're all coming to beat me up!? O-Or maybe it's an assassin or kidnapper hired by house Hevring to send a message that my family's interference in their sphere isn't going to be tolerated any longer!"

The girl's imagination spirals more and more out of control, her pace gets faster and faster, and her eyes dart around frantically. Every flickering light is an arrow tip or sword reflecting the moon, every corner hides an assassin, every noise she makes is too loud, every step she takes isn't fast enough, she's expecting a dagger or arrow in the back any second now.

Bernadetta actually misses her doorway due to how fast she's running. She skids to a halt, frantically pulls her key from her pocket, and practically dives into her dorm room. She slams the door shut, locks it, and collapses against the wall.

Only now, safely in her room (never mind that a wooden door is the only thing separating her from any potential assailants, or an easily-breakable window) does Bernadetta start to calm down enough to think with a measure of rationality. She goes through the motions of putting away her art supplies, wraps her painting in a small protective blanket, all while thinking about the narrow escape she just made... or how much of a fool she was.

"But what if it wasn't a killer or someone trying to hurt me?" She asks herself. "What if it was Caspar, but he wasn't mad, and now that he's seen me running around like a maniac for no reason, he'll think I'm suspicious, and then he'll actually try and kill me!"

All this goes through her mind as she changes into her nightclothes and go to sleep. When she turns to actually look at her bed, however, she sees something that makes her heart stop.

There, sitting on her bed, is a note, along with a paintbrush. Her paintbrush. One she must have left behind in her rush to leave.

That means whoever found the paintbrush managed to get back to her room, and get into her room despite not having a key, and had time to write a note, before she ever opened her door.

"You forgot this! Nice painting by the way, I like how you brought out the reds around the edge of the sun. - B"

Bernadetta doesn't remember anyone else coming around where she was painting. They even got close enough to pick out specific details, and she never noticed. They could have been peering over her shoulder for who-knows-how-long and she would have had no idea.

That's quite enough for Bernadetta. Her legs buckle, and she faints into her bed.

###

"Training?"

"Gods!" Caspar whirls around, his heart suddenly pounding. "Teach? When did you get in here? Were you here all along?"

"No, I walked in just a minute ago." The lady smiles innocently.

"I didn't hear you come in at all!" Caspar laughs. "You're quiet!"

"Thank you. It's very useful in stealth missions." Byleth says sweetly. "Especially assassinations."

A chill passes down Caspar's spine. "O-Oh, uh, that's cool."

"Indeed."

"So… what are you here for?"

"I was just planning to run some simple drills, that's all." Byleth hums. "You don't mind sharing the space, do you?"

"Of course not!"

Byleth set aside her usual weapon, an unfamiliar single-edged sword that looks to be of foreign make with a circular guard and tight red wrapping on the hilt, and picks up a training sword instead and drags a new dummy to one side of the training pit.

Caspar turns his back to his professor as he goes back to his own training. He has metal training gauntlets on, but he's been unsuccessful in dealing any lasting damage to the training dummy. He can only attribute it to his lack of strength and lack of training.

"Thunk!"

Caspar pauses, and turns around. He blinks in surprise at seeing the training dummy his professor had taken out just a minute before now minus a head. The neck, a solid two-by-four, is completely shattered, and apparently in one strike.

Byleth, ever smiling, just says "oops!" and goes to get a new dummy like shattering a dummy with a wooden training blade is something normal.

Thoroughly unnerved (and a bit annoyed at his own lack of strength compared to his teacher's effortless power), Caspar decides to call it quits for the day.

###

"Hello class."

Everyone freezes for a moment. Conversations stop, and heads whip side-to-side looking for the source of the voice. Petra cranes her neck to try and look behind the curtains, Ferdinand checks the nearest pillar, and Bernadetta even looks behind her at the closed classroom door.

All the students thought their professor was running late, but apparently that's not the case. She's already in the room, but no one can see her.

"Today, we'll be learning about observation and stealth."

There's a quiet creak, followed by a loud "WHAM!" and a yelp as Byleth lands heavily on Edelgard's desk, causing the princess to shout in shock and fall from her seat. Even Hubert, normally the stoic, recoils in his seat from surprise.

There's a long pause as everyone stares at their teacher. She casually brushes off her cape descends from Edelgard's desk. The princess still hasn't gotten off the floor and is gaping with bug-eyed shock at her professor. It's only when Hubert starts to help her up that she comes to her senses and returns (shakily) to her seat.

Someone finally finds the courage to speak. Ferdinand. "Were… were you in the rafters? How did you even get up there!?"

"I climbed the pillars of course." Byleth says as if it's obvious, all while smiling. "Although, I suppose I also could have climbed the curtains and jumped to grab the rafters from there, or even leapt from my podium. The doorframe is also an option, though it's a bit narrow. The fireplace is good, provided it's not too hot or you have heat-resistant boots and gloves."

"Erm…"

"You'd be surprised what you can do with good balance, a solid jump, and strong grip." She remarks cheerily. "Anyways, first lesson of stealth and observation: people seldom look up!"

Edelgard, who has just barely recovered from her near heart-attack, puts her head down on her desk. "Please don't let every lesson in the unit start like this. I won't survive that long."

###

She may be smiling, but Linhardt has the distinct feeling his professor isn't as happy as she looks. That's a fair assumption considering he doesn't think anyone in the Black Eagles has seen Byleth not smiling, so a smile may as well be a blank stare for all it tells anyone about how she feels.

He wouldn't call her scary, but the total inability to read guess what she's thinking is very unnerving. Intimidating is a better word, maybe even creepy in some cases.

"What is it professor?" Linhardt yawns to try and hide his nervousness. "This is cutting into my nap time."

"School matters are cutting into nap time?" Byleth murmurs. Linhardt isn't sure if it's his imagination or not, but her smile seems to grow a fraction. "I see…"

The green-haired boy shifts uncomfortably in his seat as his teacher grins down at him from behind her desk. Her hands are steepled, adding to the somewhat sinister aura she's giving off. Linhardt swallows thickly, and averts his gaze for a moment as he's unable to take the pressure.

When he looks back, he finds Byleth's face only a centimeter from his own as she's learned all the way across her desk. Linhardt freezes instantly and his eyes go wide. He didn't even hear her move. Her smile is as wide as ever, but it doesn't reach her eyes.

"I don't mind if you sleep during class if you think you know the material, but I expect your assignments to be impeccable if you choose to do that." She says quietly. "Understood?"

Linhardt swallows thickly. "Y-Yes Professor Eisner."

###

"S-Sorry, I have to go… uh… rotate to the next position." The guard stammers, and quickly scurries away.

"Geeze Professor, you really showed him what-for." Dorothea, who had apparently been watching the whole thing, steps out from around a corner after the guard is far enough away. "What did he do to deserve that? Something horrible?"

The lady, always smiling, turns to face her student. "What do you mean?"

"I'm not sure what you were saying, but you were totally up in his face! You had him backed against a wall, were leaning over him, were cutting off an escape with one of your arms, not to mention that super-wide and unhinged smile you had on. You really wanted to scare him, didn't you?"

"Oh, uh, no."

Dorothea blinks. "No?"

"No. I didn't."

Now she's almost afraid to ask. "...then what were you going for?"

"I was… flirting."

Oh. Oh. Oh… Wow. Dorothea has never seen someone fail so badly at flirting in her entire life. Even an awkward boy who's never flirted before has more hope than Byleth. If Dorothea hadn't known better, she honestly would have assumed her professor was trying to extort the man, and she already though the lady was chewing him out for something.

Taking a deep breath, Dorothea steps forwards and put her hands on Byleth's shoulders. "Professor. Smile for me."

"I am smiling." Well, that's true, she's always smiling.

"Look less stiff about it." Dorothea clarifies. "Not a polite smile, a genuine smile."

Byleth's smile becomes even wider, showing the barest hint of teeth. The problem… well there are several. The smile is just wide enough to look unnatural, her brows are slightly furrowed so it looks like she's leering, and she's now leaning slightly forwards so as to ever-so-slightly be invading Dorothea's personal space.

It doesn't look genuine. It looks like Byleth is planning her murder while smiling in her face.

"Okay… I have my work cut out for me…" Dorothea thinks, sporting a forced smile of her own so as to not hurt her teacher's feelings. "Uh, you can stop now."

Byleth does so, and her face returns to the usual placeholder smile. Her student subtly breathes a sigh of relief.

"Goddess above that's terrifying. That poor guard… How did this women learn to flirt!?"

###

"There's two of them." Hubert groans.

"Whatever do you mean?" Edelgard frowns, and looks up from her papers.

"Professor Eisner. There's two of her now. It would seem Petra is learning her techniques." Hubert says as he massages his forehead and takes a seat. He points to the window. "You can see for yourself if you care to."

Edelgard really doesn't want to know… but at the same time, as the representative of the Black Eagles, it's her duty to stay on top of everyone's skills and any new developments in any of their lives. She reluctantly pulls herself out of her seat, walks to the window, and peers out.

"Hubert."

"Yes Milady?"

"Please tell me I'm not seeing-"

"You are." Hubert interrupts in a defeated tone. "You are."

Edelgard doesn't want to know why Byleth and Petra are sneaking across rooftops, jumping into trees, and practicing silent landings (which inevitably involves scaring the life out of anyone unfortunate enough to be in the area as they become test targets for the pair's stealth… or more particularly Petra's because Byleth is already a master).

"I'm going to be looking over my shoulders constantly now, aren't I?" Edelgard thinks, and massages the bridge of her nose. She shakes her head and returns to her papers, only for another thought to occur to her a minute later. "Bernadetta is going to be more paranoid than ever..."

…

"Wait. Professor Eisner is amazing at silent landings. That means she intentionally scared us during that lesson." She realizes. Her eyes narrow. "Maybe that permanent smile of hers is a sadistic one..."

###

"Professor… I have a question." Ferdinand says. It's currently lunch break, and the teacher saw fit to join her students in the mess hall.

"Hmm?" Byleth raises an eyebrow, smiling… encouragingly? Or maybe that's her normal, neutral smile. It's hard to tell with her.

"Did you, perhaps, undergo noble etiquette training?" The boy asks curiously. "Some of your behaviours seem to suggest that you have. You can speak very elegantly when you choose to do so, you walk with a straight back and your head held high, and you always have a polite smile. All very noble-like behaviours."

Of course, her tendency to casually climb buildings for no particular reason, never knock or announce her presence, and a number of other things rule out the possibility of full noble training, but she does seem to possess some level of high-class education.

"Ah, that." The lady hums. "Yes, I learned that when training to be an assassin."

Ferdinand blinks in surprise. "Pardon?"

"One of my father's mercenaries is a former assassin. He allowed her to teach me her skills." Byleth says simply. "A lot of it involved disguise and being able to behave in an unsuspicious manner. Of course, I'm not making a particular effort to disguise myself, but seeing as I'm of somewhat high station now I'm borrowing parts of that training so as to not cause a fuss."

"Ah…" Ferdinand says slowly. "Is that right…?"

"Yes."

Byleth's idea of "not causing a fuss" is clearly wildly different from his, Ferdinand decides. Because casually leaping down from rafters and scaring all you students, not to mention having everyone in the monastery at least mildly afraid of you due to your permanent unnerving smile and tendency to show up out of nowhere and without warning, is not Ferdinand's idea of "not causing a fuss".

"If you were to put on your full disguise, so to speak, what would it be like?" Ferdinand inquires.

"Hmm…" Byleth thinks. She takes a moment to compose herself, and Ferdinand realizes she's going to show him. Her smile softens to something less stiff, she clasps her hands, pushes her legs together, and makes sure to keep her back completely straight. Her clothing doesn't reflect it, but her posture is the perfect picture of an attentive young noble girl. "Greetings Lord von Aegir. It's a pleasure to meet you. I'm Byleth Eisner, daughter of Sir Jeralt Eisner. I do hope we can get along."

It's almost eerie how perfectly she captures the personality of a generic minor lady. Ferdinand didn't think someone as… unique as Byleth could manage it. "That's quite impressive."

"Thank you sir!" Byleth giggles. She leans forward slightly, tilting her head innocently while subtly thrusting her chest forward. "You give me far too much credit, I'm had plenty of help to develop these skills. I had to learn to talk fancy, how to hold myself, how to seduce, and so on. Of course, small talk is also a part of it. Perhaps you'd like to discuss the state of the empire and the ongoing argument between houses Varley, Hevring, and Bergliez? Or perhaps, Sir Aegir, you want to regale me with tales of your deeds and how you're better than Miss Von Hresvelg?"

Ferdinand now knows he's being mocked. "You say that as if I do it often."

"Oh, my pardon, I didn't mean to offend." Byleth gasps. She grabs one of his hands in hers. "Please sir, I apologize."

Ferdinand is slightly creeped out now. "Erm…"

"Incidentally." Byleth says, dropping her sweet fake voice. "You're very dead."

"What?"

Suddenly the professor pulls sharply on his hand, forcing him to lurch forwards into the table. One of her hands snaps out and grabs him firmly by the neck, just under his chin. Her fake smile is gone, replaced with her usual unreadable one. "If I had used a knife, you'd have a slit throat right now. Or I could just strangle you now that I have the upper hand."

She releases him, and Ferdinand sits down hard in his seat. His blood is now pounding, and his breathing heavy.

"Consider that a preview of our next unit on deception." Byleth says neutrally. "Perhaps you would like to help me with the initial demonstration? I usually use Edelgard."

The "without her consent" is implicit. Considering how Edelgard usually ends up traumatized, Ferdinand isn't very enthusiastic about the idea.

I hope you all found this entertaining. I tried to keep the core of what I think Byleth is: social incompetence and an almost total inability to be read emotionally. I just executed it in a different fashion this time. F!Byleth isn't quite as simple as M!Byleth, but what she lacks in brutal bluntness and complete obliviousness she makes up in having zero concept of personal space, and having no idea how scary her incredible stealth skills, strength, and permanent smile can be… as well as having learned to flirt by watching her father's rough-and-tumble mercenary company hit on barmaids and whatnot and try to emulate that, meaning not only is she attempting to play the usually male role but she's mostly only seen the most crude and aggressive flirtations and therefore only has those for reference. (And, incidentally, she considers the seduction she learned from assassin training to be "fake" or "insincere", hence why she doesn't just emulate that).

This was so much fun, though I'm not sure if it's quite as good as Byleth:Peculiar Professor. Humor is not something I usually do, so I'm still finding out what works. I do realize this version of Byleth isn't quite as faithful to the game, but I hope you enjoyed it all the same.