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

Blue lions… okay, let's do this. Hopefully this will be a bit easier than Peculiar Professor, because this version of Byleth isn't quite as reliant on the quirkiness of other characters to facilitate her own strangeness. She's a bit of a menace, and being a straight-man doesn't mitigate that.

Hopefully.

Dimitri thinks there's something very off about Professor Byleth. She seems relatively normal. She's friendly, intelligent, and always has a smile on her face. Always, as in it never ever drops. She never has a neutral expression on her face. Not when teaching, not when marking papers, not even when scolding someone. Her face seems locked like that. It's only now, after two weeks, that the sheer weirdness of this behaviour has started to be noticed by him and his classmates.

"I never see her around campus." Annette notes quietly. "She's always here before everyone else. I even came really early once, just to see if I could beat her, and she was here waiting at the desk, looking like she was expecting me."

"I do not see her leave." Dedue offers. "Not once. I do not wait necessarily… but on the chance we stay around the outside of the classroom after class for some reason, I pay attention. She doesn't leave through the front. I have gone back inside to get lost items, and she'll usually be gone."

"Wait, she'll be gone, but never left through the front door?" Annette clarifies.

"Yes." Dedue nods. "It is… unnerving."

"Have you ever noticed how quiet she is?" Ingrid adds. "Remember that quiz we were writing two days ago? I raised my hand for a question while still looking down at my page… I didn't realize she'd walked over until she cleared her throat. She was directly beside me."

"She's also has a peculiar way of dressing, and I don't say that to be mean." Sylvain adds. "Her attire is quite... unique. She shows quite a bit of skin as well."

"Of course you'd focus on that." Ingrid snorts.

"Excuse me! She's an attractive woman." Sylvain huffs and crosses his arms. "And her outfit draws attention to her features as well! Her attire doesn't exactly downplay her chest or legs. Quite the opposite."

"That is a fair point. It's another peculiarity of hers." Dimitri nods. "Even professor Manuela is a bit more… erm… classy about her choice of dress. Not that I think the professor is doing anything too inappropriate, but her choice of dress is rather outlandish."

"She is the daughter of Jeralt Eisener, and she is instructing us on combat readiness and such." Felix adds suddenly. "And so it makes sense that there are signs of her being a trained soldier in her movements, but… there are other things as well. Have you noticed how she has her podium in the corner of the room? She seldom puts her back to the windows or the door, and so I think she moved it there to facilitate that."

"Now that you mention it…" Ashe says slowly. "I see elements of a thief in her too. She's always scoping out the class. I've seen her eyes focus on Annette's earrings, people's pockets that have an obvious bulge like someone looking for a wallet, and she also notes everyone's weapons each time we come in." He glances at Dedue. "She always looks at your first, and always checks that you have your axe."

"I see." The dark-skinned man shifts in place, clearly a bit unnerved by this information.

"I think she's rather nice." Mercedes offers. "She's very helpful."

"I won't argue with that." Dimitri agrees slowly. "She's just… unusual."

"I hear she's also a trained assassin." Someone says.

"Really?" Ashe blinks. "Wow, that would explain a lot actually."

"Indeed. It would explain why she's so good at scoping out a room…" Dimitri nods.

"And her ability to leave unnoticed." Felix adds.

"Wait…" Mercedes frowns. "Who said that…?"

Sylvain frowns. "Annette?"

"Nope."

"Ingrid?"

"No."

"You're all terrible at noticing things." The voice says. "Look up."

Everyone does so, and many of them blanche upon seeing the person they were just talking about casually sitting in the rafters above their heads. Her legs are crossed casually, and she's smiling down at them with her usual unchanging expression.

"Really now, I thought I taught you all better." She says in a scolding voice. She uncrosses her legs, stretches, and drops off the ledge down to the ground. The landing, surprisingly, is almost totally silent. There's a small "clunk" as she lands, but it's only noticed because everyone is specifically listening for it. "Always look up."

"P-Professor!" Annette squeaks. "H-How long have you been here?"

"A few hours." She says calmly. "I was grading."

"In the rafters?"

"Yes. It's safer."

"Have you even left the classroom all day…?" Ingrid asks cautiously.

"Yes."

Ingrid waits a moment, expecting Byleth to elaborate, but she doesn't. Byleth just keeps smiling that same, fixed smile. It's really unnerving to everyone now that they're paying attention. The smile never breaks, never changes even a little bit, like a mask.

"An assassin you say?" Dedue asks. His brow is furrowed, obviously a bit suspicious.

"Yes." She blinks. "Incidentally, it would have been very easy to kill all of you. I have more than eight knives. You really should look up."

"Is that a threat?" Felix questions.

"No. A warning. Most assassins you meet are probably going to try and kill you." She says bluntly. "You're all nobles, or important to some extent, and so you are possible targets."

"It will not be so easy." Dedue says firmly. "If you had attacked, I would have protected Prince Dimitri."

"Right." She blinks, still smiling. "Above you, by the way."

Dedue looks up, and sees nothing. There's a round of gasps and yelps which causes him to look back down to see Byelth standing on the table they were gathered at, calmly holding a knife to Dimitri's throat. If it weren't for everyone else's reactions, Dedue wouldn't have known she'd moved before looking back. She was totally silent, and fast enough to make that move in less than a second.

"So, like I said, I could have killed all of you." She says calmly, and pulls back the knife. "Never take your eyes off a potential threat if you can avoid it."

Dedue swallows thickly. "Yes Ma'am."

"Good." She pockets the blade, crouches, and suddenly leaps several feet up into the air to grab a rafter and pulls herself back up. "Tomorrow's class we'll begin discussing combat readiness. Everyone bring their weapons and armor." She grabs a book and a quill, which were hidden behind a vertical beam leading up the ceiling. "Dismissed."

###

"Ah, Professor! I don't see you out of the classroom all that much." Sylvain greets as he takes a seat next to the woman. She's sitting in the corner of the mess hall, and has turned the table she's at so her back can face the corner rather than a window. "Have you come to enjoy the fish special today? I have. I hear it's quite the treat."

"It's fish." She smiles at him. "They simply added more seasoning than usual."

"Well, at the very least it will taste better in attractive company?" Sylvain winks.

Byleth is quiet for a moment while staring at Sylvain. Then her smile actually relaxes into something that seems much more natural. "Well, aren't you quite the charmer Sir Gautier?" She says in a tone that could almost be called a purr. "I would love it if you joined me for this meal."

Sylvain gives her a winning smile. His natural charm does it again… or maybe that's just the allure of his crest at work. He knows most women put up with his advances because they hope to gain a higher status through his crest and title rather than any actual attraction to him.

Well, he's more than willing to play their game. After all, it's not like he doesn't play back.

"We don't often see you out of the classroom." Sylvain says conversationally as he cuts up his food. "Do you hide in the rafters all the time? Or do you actually leave?"

"A mix of both. When I'm doing teaching-related things I'm usually in the rafters, and when I leave I take the back exit."

"Back exit?"

"Windows. They're good exits and entrances people don't usually think about, which makes them very useful to people like me."

"Ah." Sylvain didn't expect that. Then again, this comes from the person who casually sits in the rafters for half a day on a regular basis. "Where do you go when you leave?"

"Here, the training area, to visit my father, or just to roam around. I do roam, you all just rarely notice me." She hums.

"Well, that's a travesty I hope to correct." Sylvain winks. "You're far too lovely to go unnoticed and unappreciated!"

"I'm unnoticed when I want to be." Byleth says. She leans her shoulder against him (giving him a nice look at her cleavage he might add) and not-so-subtly rests a hand on his leg. "Although I suppose I could show myself a bit more, just for you~"

"Please do." Sylvain says with a grin. He's surprised at how easy this is. He would have expected a teacher, much less a self-proclaimed assassin, to be much more difficult to successfully flirt with. "You're too much of a beauty to go unseen."

"Sir Gautier, are you flattering me?"

"Depends, is it working?" He asks in return.

"Maybe."

"Then yes, I am."

They finish their food while trading small talk. Actually, Sylvain does most of the talking, edged on by Byleth's encouragement. They both politely ignore the curious looks that they're garnering, and when they're both finished eating, they walk out of the mess hall.

Byleth actually keeps herself pressed into his side as they walk, and has an arm looped through his. Sylvian isn't about to complain about having a shapely woman at his side, especially when it means he gets his arm pushed into her chest. That's very nice in his opinion.

"Sir Gautier." Byleth murmurs, and strokes his shoulder. "I have a place I like to visit with quite a nice view; would you like to see it with me? No one really goes there, so we'll have it mostly to ourselves..."

"That sounds fantastic." Sylvain agrees. He allows her to pull him along to one of the more unused corners of the monastery, with a view overlooking the mountain path that travels to and from the town below. It really is a nice view, and Sylvain suspects it will be doubly so in several hours when the sun sets and colors the sky in reds and oranges. "My, you know how to choose scenery professor. I may have to make use of this place myself…"

He can see this being a perfect spot to take a girl on a date. This is quite a nice tool she's dropped into his lap.

"Sir Gautier… Sylvain…" Byleth purrs his name, elongating the 'v' sound. She turns to face him directly, and presses herself bodily against him. Sylvain particularly appreciates how her large breasts squish up against his chest. Her left hand strokes his hip while the other tangles with his own hand. "I've heard rumors about you Sir…"

"Which one? There's quite a few." He chuckles.

"About how you're a horrible womanizer." She says while pouting her lips at him. It's quite the inviting sight, especially combined with her half-closed eyes. She's also putting a lot of her weight against him, which is making it a bit hard to stand upright.

"Well, I won't exactly deny that…" Sylvain says, taking a step back to regain his balance. Byleth takes a step forward to match it, keeping herself pressed right against him. He can feel hand playing with his, her fingers fiddling with his own.

"And how you have quite the weakness for a lady with a large chest." Another step back from him, another forward from her.

"What self-respecting man doesn't?" He jokes.

"And how you're very, very…" His shins meet the stone wall, but Byleth doesn't let up. The boy is forced to lean backwards, and she finally distangles her hand from his. Both of her hand them come to his shoulders, and lie there for a moment. Her pout suddenly vanishes, replaced by her normal mask-like smile. "Foolish."

She pushes lightly, and Sylvain topples backwards. His back doesn't meet the stone wall like he expected. It's a knee-high wall. He was distracted by the Professor, and never considered what was behind him. His arms flail out, trying to grab something, anything as he loses his balance; he feet leave the ground, and for a moment he's certain he's going to fall into open air.

One of Byleth's hands shoot out and grab him by the collar, stopping what would have been a several hundred meter fall down a rocky cliffside. His feet aren't on the ground, and the only other thing keeping him up is the back of his knees desperately trying to grip the wall he was just pushed over.

"That was pathetically easy." The lady says calmly as she watches her pupil flail. He grabs her arm, eyes wide with panic, pleading at her not to drop him. "All it took was a pair of breasts, and you did everything I wanted. I gave you time to react as well. I could have just as easily stabbed you as soon as we were alone. Instead I slowly pushed you over a wall, and you still didn't expect anything."

"Wh-Wha-!?"

"Did you even check if I had weapons on me?" She asks impassively, apparently content to let him dangle over a cliffside for the moment. His life in literally in her hand. If she lets him go, he's dead, and there's nothing he can do about it. "Or watch for poison? I know you didn't pay attention to your pockets, I took everything off you and you didn't notice."

Just to prove her point she removes his coin purse, his quill case, his fancy dagger, his belt, and even his family ring that was on his finger, from her pockets and drops them on the floor beside her.

"Everything." She repeats calmly. "And you never noticed, because you were too busy looking at these." She pointedly slips an arm under her breasts and lifts them a bit, as if he didn't already know what she was talking about. "Far be it for me to shame a healthy sexual interest, but you mustn't allow it to kill you."

"I-I didn't know this was a test!" Sylvain protests.

"Assassins aren't going to announce they're here to kill you. They'll just kill you. You have to look out for these things on your own." Byleth warns. "Not every lady is going to want your crest. Some will want your crest gone, and I've just shown how easy that is. I didn't use my best plan either. I could have had you dead in a minute of sitting down next to me without anyone suspecting it was my fault."

"I get it, I get it!" He squeaks. "C-Can you please pull me up now?"

###

"Gah…" Felix grunts as his teacher's sword smashes down on his. For a so-called assassin, she fights like a brute. She's overwhelming him with sheer strength rather than finesse or skill. Not to say she's particularly unskilled of course, she's clearly a good swordswoman, but she's not relying on her skill at the moment. Her battle plan is clearly just to beat him into submission.

And worse, it's working. She doesn't have quite as much brute strength as Boar (which, if anything, is a testament to how absurdly strong Dimitri is rather than any lack of strength on Byleth's part) but her edge on Boar in terms of skill and experience makes her infinitely more troublesome to beat anyhow.

Another overhead strike slams down on his blade, and he barely holds. He shoves it off to the side and tries to counterattack, but suddenly finds a boot in stomach and is kicked to the ground. He raises his sword desperately to blocked the next attack he knows is coming, but it doesn't matter. There's a sharp "CRACK!" as his wooden practice sword breaks under the sheer force of his professor's attack, and her blade smacks him harshly on the head.

"Oh, sorry." She says, and offers him a hand up. He reluctantly accepts. His head hurts, and it will probably bruise unless he gets it healed, but it's nothing of significance. He'll ask Mercedes to help after this done. "I forget how frail these weapons are sometimes."

Frail? Training swords are made to be durable and hold up to quite a bit of punishment. It's not that the weapons are frail, it's that she's stupidly strong. "If you say so Professor. You don't fight as I expected you to. You claim to be an assassin, but you fight in a quite straight-forward manner relying on sheer strength more than anything."

"I'm more than capable of doing something else, I just figured this would be the best way to beat you." She says calmly. She's smiling in his face, but then again, she's always smiling in everyone's face. Her 'mask' (as the students now call it) really is impeccable. "You have trouble beating Dimitri, who uses much the same plan, so I decided to abuse that weakness."

That stings his pride a bit, but she's right. "Now that is what I'd expect of a career mercenary. If only more knights had that mindset and were less focused on chivalry and such."

"With any luck, I'll have taught all of you to think the same way by the time I'm done with you." Byleth says. "Do you want to go again? I can fetch another sword…" She glances at her own blade, which has several noticeable dents and cracks. "...or two."

Felix doesn't want anymore bruises, to his body or his pride. "I think I'm good for now Professor."

###

Ashe actually likes sky patrol duty. It's not that he's particularly good at it, he's not very fond of pegasi or wyverns, he just likes the view from up high. He can look down upon the monastery and see the goings on of everyone below.

He's tried picking out his classmates before. Some are easier than others. With his dark skin and white hair, Dedue is the easiest. The other Lions have more generic hair colours, which is a bit more difficult to spot. People like Caspar or Hilda stick out like a sore thumb, as does Bernadetta on the odd occasion she leaves her room, purely on account of having rare hair colors.

He's managed to pick out every other Lion at least once though, so for the last few times he's been trying to find Professor Eisner. She's very hard to spot, though that might be because she doesn't leave the classroom much at this time of day, but he still tries anyways.

Today, he actually gets some success… but he doesn't spot her where he expects. She's not walking along any pathway, she's near the top of one of the cathedral's spires casually talking with another unknown woman while they exchange punches.

Yes, they are sparring atop a spire, on quite unstable footing. Ashe circles once around the building just to watch in fascination.

Apparently he's noticed though, because both women stop what they're doing to stare up at him. Professor Eisner waves, and Ashe returns it sheepishly before pointedly flying in the opposite direction.

He has quite a story to tell the others over dinner though.

###

"You're part of the church, right?"

"My word!" Mercedes gasps. She turns around to see the professor standing right behind her; so close in fact that Mercedes feels the need to take a step back to put space between them. Byleth basically had her nose in Mercedes's hair from how close she was. "Professor! I did not hear you."

"Good." Byleth says. "You're part of the church, yes?"

"No, I am merely a devout follower." Mercedes murmurs with a shake of her head.

"Ah." The teacher's reaction is hard to read considering her expression doesn't change. Just the same fake, fake smile. "Well, maybe you can still help me."

"What do you need to know Professor?"

"What is church protocol for dealing with disobedience?" Byleth asks. "As in, the rebellion of another branch of the church?"

"Is this about the Western Church incident?" Mercedes murmurs.

"Yes." Byleth says calmly. "I have realized I am insufficiently knowledgeable about the church, but asking Rhea or Seteth would get me biased answers. You are likely to be more forthright, as you hold no significant station in the church… or any station apparently."

"Well, I don't think I'm the best person to ask, but I'm happy to try and teach you." Mercedes says. "Talking religion can take a while though. Maybe this is better done over tea."

"I can do that." Byleth nods. "Can we do it now?"

"Professor… it's almost past curfew." Mercedes murmurs. "This is hardly the time."

"Oh." She glances out the window. "Right, you students don't stay up late."

"Yes… and professor?"

"Hmm?"

"You could have knocked. I presume you came in the window, but there was no need for that." She admonishes softly.

"A good assassin never comes in the front door, unless they're in disguise." Byleth responds as she opens up the window and step out. "We'll talk tomorrow. Goodnight Marshmallow."

Mercedes watches the lady leave, and closes her window and curtains after the professor is out of sight. She turns back to her desk, which she was just cleaning up after writing a small essay, and finishes that up.

One thought sticks in her mind as she goes to bed though: "Marshmallow?"

###

"Stay still." Byleth tuts. Dimitri awkwardly keeps his eyes open, and tries not to flinch away as the brush slides on his skin just millimeters from his eye. He didn't quite expect this talk to go this way. All he said was that he was tired, but that he didn't want to show a bad example to the rest of the class. He never considered makeup.

In hindsight, it makes total sense the Professor knows how to use makeup though. She's talked about disguise before in class, and recounted some of her own disguises. Of course she knows how to use makeup.

"There we go… now just don't rub it too much. You can wash it off later with water." She says as she pulls away the brush. The makeup she had put on his face before, which stuck out like a sore thumb, now blends perfectly with his skin tone… so long as you don't look too close. It's a quick and dirty job, but quite effective considering that. "I expect you to go to sleep early tonight as well, understood?"

"Yes Professor." He replies sheepishly. "My apologies. I was looking over reports from the kingdom. My regent, Rufus, deals with it all at the moment, but as soon as my education is finished I will have to take on those duties, and so I must have all the necessary information beforehand."

"I am not disagreeing." Byleth says. "Merely reminding you that your own exhaustion is just as potentially dangerous as being underinformed. You must strike a balance."

"I know…"

"Apparently not." The teacher replies flatly. "Or you wouldn't have walked in here looking half dead."

Well, Dimitri can't exactly argue with that.

"Now, I've hidden the bags under your eyes, but if you want to fool everyone you're still going to have to act not tired." Byleth reminds him.

"Of course." The prince sighs. "Thank you professor."

###

"Ack!" Annette squeaks as she tries to hold all the groceries up. She has a lot of bags, maybe she shouldn't have done this by herself…

"Need help?" A pair of hands reach around from behind her, and snag several of the bags from her hands.

"Professor! I didn't realize you were here." Annette says gratefully. "Thank you."

"I followed you here." Byleth admits without an ounce of shame. "I heard you were going on your own, so I've been escorting you."

"Oh… I didn't see you."

"I know. I was making sure not to be seen." She says flatly. "It's dangerous for a lone woman, especially a girl as young as yourself, to be walking about on her own."

Annette pouts. "Come on professor, it's just the town. It's basically a part of the monastery."

For just the barest moment, Annette thinks she can see the lady's mask fall, and the barest hint of a worried frown cross Byleth's face. It's only a moment though, and the fake smile is back up quick. "It's not safe, unless you're prepared to fight, you should be going with someone else."

"Come on." Annette huffs. "Just because I'm a girl I can't go to town on my own?"

"You can. Just be prepared to stab someone if you need to." Byleth responds curtly. "There's a reason parents worry about their daughters being out at night. This society may technically gender equal, but do not be so naive as to assume that everyone thinks that way. Some people still think in the old ways… and the old ways are considered distasteful for a reason."

Annette was mostly joking. She wasn't expecting her professor to take this so seriously. "I know Professor, but I don't want to have to be escorted every time I leave the monastery."

Byleth's face is unreadable. "That's fine… just be prepared."

"I am." Annette reassures. "I have magic after all! I can blast anyone who tries to mess with me!"

The lady nods in approval. "Are you prepared to do so though? Are you prepared to attack someone if you need to?"

"I… yes." Annette nods. "I can."

"Hmm… alright." Byleth says, sounding a bit reluctant. "Be careful."

"Of course."

"If anyone messes with you, tell me. I'll stab them."

"Please don't…"

###

"Another one?" Ingrid sighs as she opens the letter. "Oh dear…"

"More marriage prospects?"

"Yes. Not that I'm eager to choose one." Ingrid sighs. "Though I suppose I will have to eventu- wait, Professor? When did you get here!?"

"Just a moment ago. I was going towards the greenhouse." Byleth says casually. "I overheard you talking to yourself though, so I thought I'd stop by."

The two are just out the back of the dormitories. Ingrid had just returned from getting her mail, and had opened this letter from her father on the way back.

"No one good?"

"More like I'm not looking to get married quite yet." Ingrid sighs. "Though, I know it would be of great benefit to my father if I were to do so. There are many other noble houses that would pay handsomely to get my crest into their family, and we could quite use money."

"You are poor?"

"Poor relative to other nobles, though not poor by the standards of commoners." Ingrid clarifies. "I would not dare call us properly poor. It would be an insult to those truly in need."

"I see…" The teacher says slowly. "Marriage…"

"I suppose you've never had to deal with such things." Ingrid sighs. "Being a mercenary rather than a noble."

Byleth nods. "Are you… supposed to accept marriage without dating the person in question?"

"Dating for nobility is a luxury." Ingrid sighs. "Yes, I would likely not date."

"How unfortunate." The teacher muses. "Though I suppose it is not as if I have ever dated either…"

"You haven't?" Ingrid asks, sounding genuinely surprised. She figured someone as attractive as their professor would have had numerous advances made on her during her lifetime.

"No. I've tried approaching people myself, but that doesn't work. Everyone seems off-put." Byleth says. She's smiling as she always is, but there's a hint of sadness in her voice. "And when they approach me, they also back off really quickly most of the time, unless I'm using a persona."

"Maybe if you stopped jumping from rooftops and rafters it would help," The girl thinks to herself, though she doesn't say it aloud. She doesn't want to be mean. "Well, your personas are less… unique than your actual self. Perhaps others are simply… erm… not open-minded."

"Maybe…" She murmurs. "But this should not be about my issues. Have you never had a date either?"

"That's really not the problem here…"

"Ah, right, you don't want to marry. Because these men are beneath you, yes?"

"Well, not quite that." Ingrid coughs. "The issue is more that I simply do not wish to be married at the moment. I am focused on becoming a knight currently."

"Of course, of course." Byleth nods. "So… with that in mind… want to spar?"

"Will you break my weapon?" Ingrid asks dryly.

"Probably."

"Well, at least she's honest." The girl sighs. "I'd be honored, Professor."

This was more difficult than I expected as well. There's just something about the Blue Lions that makes humor difficult. It's probably because they're the least quirky/most serious of the three houses, so they lend poorly to humor and better to a proper story.

At least, that's my theory. I'm taking a guess. Maybe it's just my familiarity with the Black Eagles that allows me to do so well with them, and I'd do better here if I knew more about the Blue Lions. I dunno. Also, again, I'm trying not to reuse the same jokes, which is making things very difficult.

Whatever. I hope you all enjoyed this anyhow.