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

Updates for this story are going to be much more infrequent. I consider it basically complete as is. Anything from here on out are just extras that cross my mind.

With that said… Marshmallow. Much less comedy this time, and that's because of Marshmallow. She's one of the few characters that can interact with Byleth in anything approaching a serious manner, and I plan on taking full advantage.

"I need your help."

"With what Professor? Do you need something explained again?" Mercedes asks with a smile. "Did Dorothea say something again?"

"She informed me that I was naive, which I am clearly not as I am used to killing things." Byleth says with a straight face. "That is not what I came for."

"What then?"

"I require cake."

The older girl raises an eyebrow. "Cake? Why? Is there a party happening? Are you planning to have tea with someone?"

"No. I need bait."

"For what?"

"Bernadetta."

There's a pause as Mercedes processes this. "Why?"

"Seteth, and Edelgard, have insisted I cannot carry her to class anymore." Byleth says neutrally. "So I must find an alternative means of getting her there. I know she occasionally sneaks cake from the kitchen, so I wish to use cake to bait her to class."

"You're going to bribe her?"

"No. I will bait her, like a cat."

Mercedes sighs in amusement. "Professor."

"Yes?"

"You will not manage to get her to class by dangling a cake in front of her nose. I'm fairly sure she would be mortified by that."

A sliver of a frown crosses the man's face. "But why? I would follow a cake."

"Somehow I'm not surprised..." Mercedes shakes her head. "I think we've established multiple times that what applies to you does not apply to everyone."

"Hmm… how about cupcakes then?"

"Professor. Food isn't going to work."

"...new thread for her needlework?"

"Dangling anything in front of her nose won't work." Mercedes clarifies. She sees him open his mouth to respond, and she cuts him off. "No, holding it in front of her face, using magic to levitate it, or any other way of holding it won't work. The problem isn't the 'dangling it' part, professor."

The man's mouth clicks shut.

"Perhaps consider a more social approach?" The girl suggests. "I'm sure her classmates could get her to come to class."

Byleth nods seriously. "Understood. I will enlist their help in this mission."

"Please don't treat this like a military operation professor…"

###

Mercedes lets out a long sigh when she sees Bernadetta being carried across the monastery grounds. Not by Byleth, but by Petra… and with Byelth following behind.

That is not what Mercedes meant by getting Bernadetta's classmates to help. Oh dear.

The older girl quickly moves to intercept the three of them. "Professor! Petra!"

"Marshmallow." Byleth nods. "I took your advice."

"I can see that." She sighs. "Petra, if you don't mind, please put Bernadetta down. I'll handle the situation from here."

"You wish to transport the target instead?" Petra asks.

"Transport the-? Oh dear…" She mumbles. The professor is treating this like a mission, and Petra just went along with it. "Erm, yes, I will deal with her."

Petra puts the small, panicked girl in front of Mercedes. She then salutes the professor, and marches off to class.

"What has the Professor done to that girl?" Mercedes sighs. She glances at Bernadetta. "And this girl too…" She gently puts a hand on the girl's back and rubs circles into it. "There there, you're fine. He means well."

The girl squawks something unintelligible and cowers behind her, away from Byleth. Normally she's be wary of strangers, but a fear of Byleth has overridden that.

"Oh dear." Mercedes murmurs, and pats Bernadetta on the head. She looks to the man standing in front of her. "Professor…"

"What?"

"When I said her teammates could get her to class, I didn't mean you should get Petra to carry her instead of yourself."

"Ah." The man blinks. "Would Edelgard have been better?"

"No."

"Caspar?"

"I wasn't implying anyone should carry her." Mercedes clarifies. "I was suggesting you get help from her teammates to convince her to come to class."

"Oh."

Mercedes turns back to Bernadetta and ushers her along. "I'll talk to him alright? You go on ahead."

"O-Okay." Bernadetta replies. As soon as she's a few steps away she bolts and doesn't look back. Mercedes shakes her head.

"Professor, you're traumatizing the poor girl." Mercedes scolds. "I know you don't mean to, but you are. She's a shy girl. You can't carry her around with consequence like you can other people."

"Oh." Byleth blinks. "Should I bring the class to her then?"

"No." Mercedes says instantly. "Please don't."

"Oh."

"Just use a gentle touch, Professor." Mercedes murmurs. "You can't solve every problem by breaking into someone's room."

"I don't only solve problems through that."

Mercedes sighs. "And not by punching things, carrying people, and throwing sponges."

Byleth falls quiet. That's a fairly telling response.

"You need to learn to talk through problems Professor." Mercedes scolds.

"Oh." He blinks. "I'm not good at that."

"I know." She soothes. "But you can learn."

"How?"

"Do what I do."

"Make cake?"

"No…"

"Cupcakes?"

"Not baking."

"Sewing?"

"Not sewing."

"Have nice hair?"

"Professor, please tell me I'm not just 'the girl who sews, makes sweets, and has nice hair' to you."

"Of course not. You also make tea sometimes."

Mercedes sighs. "Anyways.. I meant that you should try to be patient like me. When you're confused about something, I listen, then explain, and repeat those steps until everything is cleared up, right? You can do the same Professor."

"Ah, I see." He nods. "So I should talk to Bernadetta, and explain that she's wrong if she tries to make excuses."

"No." Mercedes says quickly. "Oh dear, this might take some effort to explain…"

###

"Professor." Mercedes murmurs. "You look… tired."

"Perhaps, but I am not." Byleth denies.

"With all due respect Professor, I think you're lying." The girl frowns.

"You can think what you want. You're wrong."

"Am I now…?" Mercedes thinks as she sips her tea. "Hmm…"

The girl doesn't bring the subject back up for the rest of their meal, but she puts into a plan for their next tea party. She makes sure the man has nothing to do for a few hours, procures some lavender tea, finds some lightly scented lavender candles, and makes sure the treats she makes/obtains are (for once) light on sugar.

Their regular meeting starts as normal. Byleth walks in through the front door (Mercedes has learned to just leave it unlocked when she's expecting him or else he comes through the window), and they sit down to eat.

If Byleth notices the change in food or tea, he doesn't comment. The only sweet Mercedes did make was her usual cake, which is what he likes the most, so he probably just doesn't care.

She also watches his movements like a hawk… or at least, as best she can. It's fruitful though, as she notices some definitive hints of exhaustion in how he moves. There's a slowness to his reactions when she speaks to him, sometimes his fork doesn't quite hit the mark and he has to stab again, and other small details like that.

"Not tired indeed…" Mercedes thinks, and hides her frown behind a sip of tea. "I am not oblivious Professor. Luckily for you." She sets down her cup and folds her hands in her lap. "Professor, I have a question."

"Mmm?" Byleth says through a mouthful of cake. He swallows. "What is it Marshmallow?"

"Last time you told me you were not tired, but I have spotted a number of signs to the contrary." Mercedes says calmly. "Professor… I don't appreciate being lied to. I understand you are shy-"

"I am not shy." The man insists with a visible frown.

"Perhaps you are right. Insecure is a more appropriate term." Mercedes nods. "You vehemently resist showing any sort of weakness."

"That's strength." Byleth disagrees. "If you show weakness, people can and will take advantage of you. You do not tell a brigand where you are weakest so he can stab you there."

"Are you suggesting I am a brigand Professor?" Mercedes huffs.

"No." Byleth says. His eyes narrow. "Are you?"

"Of course not." She denies. "Professor… what makes you assume I will metaphorically stab you if you show weakness?"

"Maybe you want me eliminated so you can become a professor, or to help someone else become a professor, or because I've worked against you in the past even if I don't realize it, or maybe you just want to steal my money, or maybe you've been hired to kill me, or-"

"Professor. Those are all foolish reasons, and you know it."

"There is no such thing as a foolish reason. People are petty. Murders happen for far less all the time."

"And you think I will kill you?"

"Maybe." He says flatly. His eyes narrow as he scrutinizes her hair. "You might keep poison in your hair…"

"I thought we were over that Professor." Mercedes sighs. "Do you honestly think I'm going to poison you, or stab you in your sleep?"

"...maybe."

"Professor…" She doesn't bother to hide the disapproval in her tone.

"A mercenary cannot be too cautious." He insists. "I cannot be careless, even around students. You are adults, or almost so, and therefore you are potentially dangerous."

"What happened to me being just sugar?"

"...poisoned sugar."

The girl clicks her tongue. "Professor, now you're just being absurd."

Byleth doesn't argue with that, but he doesn't seem to be backing down either. Mercedes is frustrated. The fundamental problem here is that Byleth deals very poorly with emotional appeals, and apparently never learned what trust was.

She needs to have a talk with Captain Jeralt at some point.

"Professor." She says firmly. "Please stop this foolishness. I am not looking for means to kill you. I promise."

Byleth frowns. "I cannot appear weak." He repeats. "I am a mercenary."

"No, you are a teacher, and more importantly, human." Mercedes insists.

"I'm a demon." He corrects.

"Even so, you cannot be stoic all the time professor. And you need sleep." Mercedes insists. "In fact, you will not leave here today until you sleep!"

His eyes narrow instantly. "How will you enforce that?"

"Professor, I'm not going to fight you if that's what you're implying." Mercedes sighs. "I'm concerned. You are clearly exhausted. I will report you to Seteth and your father if you fail to take care of yourself."

Byleth's expression can only be called a sulk.

"I'll take that as a 'yes Mercedes'." The girl says triumphantly.

"Marshmallow." He mumbles. "I wouldn't say your name."

So she's noticed. It's curious to hear him say so though. She assumed it was subconscious that he always used a nickname for her. Apparently not. She has to wonder why, but that's a conversation for some other time.

"Well Professor, if I've made my point…" She gestures to the bed. "Sleep. You need it, and I know you don't have anything to do until dinner, so don't try to wiggle out of it."

"I can do that in my own room."

"Oh no, I'm not giving you a chance to get away. If I'm not here to make sure you rest, I know you're going to ignore me." Mercedes huffs. She points to the bed again. "Sleep."

Byleth reluctantly complies, scowling at her the entire time. He removes his heavy coat, armor, boots, and weapons. He actually looks a lot smaller without them on. He was never bulky to begin with, but the loose coat and armor added an inch or two on his shoulders and upper body. He's not skinny, but he's certainly on the thinner side.

Before he lies down, he stares at Mercedes and says. "Can I at least…?"

Mercedes doesn't understand for a moment, then laughs. Sometimes he's a stoic mercenary, and sometimes he's surprisingly childish. She leans forwards and allows him to weave his fingers into her hair. This time he even leans forward to rest his head against it for a second. The joy of simple pleasures, Mercedes supposes.

Finally, Byleth lies down in the bed. Mercedes draws the curtains over the window, leaving just a sliver of light in the corner of the room where a chair sits so she can do some sewing.

Yes, she is going to sit here until she's positive he's actually sleeping. Yes, she does think this is an appropriate course of action considering who she's dealing with.

###

"Professor, you may want to consider getting a second outfit." Mercedes says as she sews up the tears in his coat. "You can't very well go shirtless every time you get a tear or your coat gets wet."

"I don't see the problem." The man says.

"Well that's not a surprise." The girl chuckles. "But other people are not as ambivalent to appearances as you."

Byleth frowns. "Is this what Dorothea keeps mentioning?"

"Hmm?"

"Dorothea keeps mentioning that I am naive, smooth, and other such things." He says. "But she always fails to explain what she means."

"I see…" Mercedes says slowly. How does she approach this? It's no secret that Byleth has the romantic and sexual awareness of a smarter-than-average log. Is it really her place to tell him? It seems like something better left to Captain Jeralt… then again, maybe the reason Byleth has that total lack of awareness is because Captain Jeralt couldn't explain things so well, or was too embarrassed to do so.

Well, he's an adult. He should know, and has a right to… and to be honest, if anyone is going to explain it, it's probably going to be her.

Taking a deep breath, Mercedes steels herself for what might end up being an awkward conversation.

###

Mercedes may have broken him.

"So Dorothea was… flirting."

"Yes."

"Which means she was either expressing a sexual or romantic interest."

"Or teasing." Mercedes reminds him. "But yes."

Byleth stares at the wall. "Sex is not just for reproduction."

"Yes." That was by far the most surprising thing Mercedes had to clarify. Somehow Byleth was under the impression that sex only served the purpose of making children. He had never been told that pleasure was a thing. She actually has some major concerns now about what his plan for taking Edelgard out to a bar entailed now if that was something he thought. More likely he just didn't think it through. For all his paranoia, he doesn't always put enough thought into things that aren't fighting.

"And love is… romance is…" He makes some stilted hand gestures, and his brow furrows. "A connection… more than friendship?"

Mercedes feels quite bad actually. She'd always had her suspicions, but this seems to confirm her suspicions that Byleth is a bit emotionally immature. Maybe Jeralt is to blame, or maybe it's just his generally odd personality, but either way her heart goes out to him. "Yes Professor."

"How do you know the difference?"

She smiles at that question. It's a childish question in a way, but an important one. "It's just something you know Professor. A different feeling in your gut. A different connection. It's not something describable. Think of it like… the difference between red and blue. You can't describe it, it just is."

"Right." He frowns. "Right…"

"You don't have to understand it now professor. You'll start to understand when you feel it."

"Okay." He takes a deep breath. "And the problem with me having my shirt off all the time is because other people think it too revealing, and things are too revealing when they look too sexual?"

"It's a bit more complicated than that, but for your case, yes."

"And when Seteth wanted me to stop people approaching Flayn, he was attempting to stop romantic advances?"

"Yes."

"Because he thinks she is too young?"

"Yes."

Byleth nods, but his brow is still deeply furrowed. He's clearly still trying to process everything he's learned. It's a good thing this is the weekend, when they both have time off. That's probably a good thing. Byleth just learned in fifteen minutes what most people slowly assimilate over multiple years.

"Professor." Mercedes murmurs. "By the way, it may be a good idea to not mention this discussion to others."

"Why not?"

"Mentioning that you had a discussion about sex with a student may not go over so well."

"That isn't the only thing we talked about."

"Others won't care Professor. They also won't care that I was the one teaching you and that nothing physical happened." Mercedes murmurs. A smile creeps onto her face. "There are many people fond of gossip Professor, and the church likely won't appreciate the bad light it will cast them in."

"Ah." He nods in understanding. Rumors. Those he can understand. After all, his title, the Ashen Demon, started with one of those.

"By the way… I was hoping to talk to your father. Do you know a time when he would be free?"

"Jeralt?" Byleth blinks. "He usually has some free time just before dinner."

"Alright."

"You need to talk with him? Is something wrong?"

"Not exactly. I simply want to discuss a few things with him."

"Okay."

"I've finished you coat by the way." She holds out the patched coat, which he takes. "I'll see you tomorrow for our usual teatime Professor. If you have anymore questions I'll gladly answer them then. Don't stress too much in the meantime, alright?"

"Okay."

"And get enough sleep! Or I will make you sleep here again."

"Fine…"

###

"Ah… you're Marshmallow, right? Byleth tells me about you."

"Mercedes. Yes." The girl says, and gives the man a polite bow. "I need to speak with you Captain, do you have a few minutes to spare? I was told you were likely free during this time."

"As long as it's not too long. I'm going to have dinner with Alois."

"It won't be more than fifteen minutes at most, I promise. I just have a few questions and concerns pertaining to your son."

"Ah." Jeralt's expression becomes more serious. "Alright then, come inside."

Mercedes gracefully steps into the room. Sets of armor adorn one of the walls, though Jeralt's own armor is kept on an armor stand just next to his desk. A bookshelf lines another, and a showcase of various trophies another. Mercedes doubts most of the things here are actually Jeralt's.

"Sorry if I don't have a tea table here." Jeralt says as he drags his chair out from behind his desk so they can be properly face-to-face without the huge table in the way. They're talking as equals here, not as the Captain and a student after all. "Erm… so what is it? Is there something wrong with the Kid?"

"Not exactly, though I'm hoping you'll tell me if there is." Mercedes says calmly. "I had a conversation with him today."

"Really?"

"Yes. A very special conversation, actually."

"Really?" Jeralt raises an eyebrow. "How so? Don't tell me he proposed."

"Oh heavens no." Mercedes shakes her head. "I'm not sure he would have properly understood the weight of a proposal before today anyways."

"Before today?" The Blade Breaker frowns. He leans forwards. "What exactly did you two talk about?"

"It came to my attention…" She murmurs. "That your son was woefully uneducated in matters of romance and sexuality, and so I took it upon myself to explain things to him."

Jeralt blinks once, twice, three times. "You… ah, shit." He leans back and stares at the ceiling. "Well, I suppose an apology on my part is in order."

"Maybe." Mercedes murmurs. "I am quite concerned at how little he knew. Did you never explain things to him?"

"I didn't think I needed to." Jeralt says honestly. "I gave him 'the talk' and all that, but he never seemed to care one way or another for romance and all that, so I never brought it up. No need to make his life more complicated unnecessarily, you know?"

"He thought sex was only for making children."

Jeralt grimaces. "That bad?"

She nods silently.

"Well, uh… geeze, sorry." Jeralt sighs. "I guess I took for granted how much I knew. Kid always seemed so smart and never asked questions, so it never occurred to me to explain that sort of stuff. I thought he figured it out on his own from listening to the other mercs."

Mercedes debates bringing up that Byleth tried to take Edelgard to a bar precisely because he paid attention to other mercenaries, but decides against it. That's a topic for another time.

"I suppose I owe you some thanks for taking care of my kid then." Jeralt says sheepishly. "So, uh, thanks."

Mercedes sighs. She should probably be a bit more frustrated or indignant on Byleth's behalf at Jeralt's less-than-adequate teaching… but to be fair, she doesn't know his whole situation, and by all accounts Byleth must have been a weird kid. Jeralt certainly could have done better, but it's not like Byleth is a total mess, and more than half of his quirks aren't even Jeralt's fault.

"I'll accept your thanks." Mercedes sighs. "Though please, if there is anything else you might have forgotten to tell him about or clear up… please do."

"Noted." The man coughs in embarrassment. "Uh, thanks Marshmallow."

"Mercedes."

"Pardon?"

"My name is Mercedes."

"Oh. My kid always refers to you as Marshmallow."

"I am aware, though I don't know why."

"Nickname huh? Unusual for him to give out one of those."

"I'll take your word for it." Mercedes murmurs, and stands up from her seat. "That will be all. It was a pleasure speaking with you."

###

"Oh my, this is quite high…" Mercedes murmurs. "Are you quite sure this is safe?"

"I haven't fallen off."

"You also have much better balance than me Professor."

"It's flat. Mostly." His expression, which has become much less rigidly flat of late, changes just a bit to concern. "We can go back."

"No, this will be fine." Mercedes decides. He put in some effort to set this up after all. It's nice and sunny, not windy, and he was the one to procure the food this time. Sure, they're on the roof of the cathedral, which is not what she would usually consider safe, but Byleth won't let her fall. They are on a flat part of the roof too, the view is nice, and getting up here was a bit of a trial in itself, so it would be a shame to waste this. She had to get piggybacked as Byleth climbed up wall (which apparently he can do. Mercedes was not aware of that. It makes sense in retrospect though, he has mentioned getting into places through the chimney before).

The spread of food is more limited than what they would usually have because Byleth provided the food this time, and it's a more barebones meal: cheese, salted meat, a few pastries, bread, fruit, and tea. Mercedes can't complain though. It's not like the food doesn't taste good (even if she bemoans the lack of sweets), and the view is fantastic.

"Oh my, it seems the sky watch has noticed us." Mercedes giggles. She waves cheerily to Ingrid and Claude who fly above them on pegasus and wyvern respectively. Ingrid seems bewildered, and Claude is highly amused. The boy gives Mercedes a cheeky, encouraging thumbs up and ushers his chore partner off to patrol elsewhere.

Mercedes can already predict the rumors that will be going around tomorrow. Oh dear. She may as well enjoy this while she can then.

Marshmallow is just too good. I can't resist using her. She works so well with this version of Byleth because she allows him to be more than just a joke character by actually addressing his personality and the problems it might present.