Disclaimer: I do not own Fire Emblem: Three Houses or its characters, I only own Blythe, Celine, and the changes in the plot that I make in the war phase.
Enjoy!
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Last Time:

Before Dimitri left, Byleth called out to him. "Dimitri, hold on for a second."

Dimitri turned to look at Byleth with an inquisitive glance. "Professor? Is everything alright?"

"I have a favor to ask you." Byleth said to Dimitri. The blond-haired prince nodded to signify his attention. "Can you keep an eye on Blythe for me during the mission? She puts herself before others, and that can sometimes put her in danger."

Dimitri nodded, his blue eyes filled with resolution. "I was going to do that anyway. Blythe is one of the closest friends I have, and I won't let anything happen to her. Not on my watch."
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13th of the Harpstring Moon, Garreg Mach Monastery, Blue Lions Classroom (Late Morning), Imperial Year 1180

It was another day for lessons, so all of the Blue Lions were inside of the Blue Lions classroom. Byleth had a more serious face than he normally did during lessons, so most of the class came to the conclusion that Byleth was going to announce something important. Byleth hit the piece of chalk that he held in his hand on the corner of the chalkboard, his signal for the class to cease any conversations that were going on. “Now that you all have the recommendation for the class that I want each of you to pursue, we now will move on to training for the mission. Yesterday, I spoke with the Captain of the Knights of Seiros, and both of us came to an idea.”

”Why did you speak to Father?” Blythe questioned while she tilted her head curiously. She looked to her left, then to her right, to see if Celine and Dimitri had any ideas. Both Dimitri and Celine shook their heads in reply, they had no clue why the teal-haired Professor would talk to Jeralt about training. The rest of the class was at a loss as well. Byleth drew a battle situation on the board before turning to the class. "The Captain and I have set up a mock battle for you all to participate in. It would be your first experience as a cohesive unit against an organized enemy, which would be valuable experience for you all. Experience that you will need before the mission."

The Blue Lions listened with rapt attention. They wanted to know more about this mock battle that had suddenly been scheduled for them. Byleth, seeing that he had all of his class's attention, continued his explanation. "The battle will take place on the 18th of this moon. I have also arranged a way for you all to gauge your authority over a group of soldiers. You all will get more information about that in the coming days. Nevertheless, more of our lessons will start to take place in the training ground, since practice is needed before the mission."

"Professor?" Ingrid said while raising her hand up in the air. Byleth looked at the blonde-haired Galatea, and gave her a signal to say that she could continue her statement. “Will the training ground sessions be with training weapons or real weapons?”

”I will not force you all to use real weapons.” Byleth started to say. He then sighed while continuing his statement. “However, real weapons will take some getting used to. We will need to use real weapons on our mission, so it will be best to be prepared.”
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15th of the Harpstring Moon, Garreg Mach Monastery, Training Ground (Early Afternoon), Imperial Year 1180

Celine, Blythe, and Byleth travelled to the training ground, about a half an hour before Byleth's training ground session with the Blue Lions was scheduled to begin. Byleth spoke to the training ground monitor, and the three of them then entered the training ground. The teal-haired professor asked for Blythe and Celine’s help for this lesson, since he knew that they were used to wielding real weapons. Byleth could also see that most of the noble Blue Lion students have experienced combat with real weapons before, since it is incorporated into their demeanor. He figured that a spar between him and Blythe or Celine would be a good way for the class to see how real weapons are supposed to be used in training.

The Eisner siblings, both biological and adopted, brought out real weapons for each of the Blue Lions students.  There were four lances, two axes, four swords, and two bows. Even though there were three students who primarily used lances, Byleth wanted Ashe to start practicing with a lance. After they finished setting up the weapons and training dummies, Blythe walked over to the bows. The turquoise-haired spellsword picked up one of the iron bows and looked at it with a strained smile. “I know that some of our class aren’t used to using real weapons, and that is to be expected. Even so, a few of them might show an unwillingness to use real weapons, especially Mercedes. I don’t want to know how this mission, or any subsequent ones, will affect Merce.”

Celine put her hand on Blythe’s shoulder, and gave her a reassuring smile. “They’ll be alright. After all, they have the rest of the Blue Lions to help.”

”You’re right, Celine.” Blythe responded. She then had an idea, which was shown by her briefly widened eyes. The spellsword turned to her brother, who was watching Celine and her converse. “Though, By, I have a small request. When you partner us up for the part of the lesson that you were doing pair sparring, can I be partners with Mercedes? I want to see if I help her get ready for the mission.”

Byleth ruminated his options for a few seconds, and then nodded to say that he was alright with Blythe being Mercedes’s partner. He could easily adjust the training pairings to fulfill Blythe’s request. Blythe smiled at Byleth, joy filling her at Byleth’s agreement. Blythe put down the bow in her hand, and picked up an iron sword. Celine and Byleth followed her example as the door to the training ground opened. The Blue Lions walked in, with Dimitri and Felix in the front of the group, and Annette and Mercedes in the rear of the group. After seeing that Blythe and Celine were with the teal-haired professor, Ingrid and Sylvain’s inner questions about the two girls’ location were answered.

Byleth was about to begin the lesson, when he heard the cry of a bird pierce the air. The Blue Lions looked up to see a hawk flying above the training ground. It flew over Blythe and Mercedes, before heading back up into the air. After the hawk left with its final piercing cry, Byleth began his practical lesson. “Now, as you all know, the mission will involve us using real weapons. To get you all ready for the mission, I am now going to begin to teach you weapons with how my father taught the mercenary group. That is with real weapons.”

”I am now going to show you an example of how Father trained us with real weapons.” Byleth said before turning to his adopted sibling. “Celine, if you would?”

”Of course.” The blue-haired swordsman responded while stepping up to where she was across from Byleth. Blythe stepped back to where Dimitri and Mercedes were in the group of Blue Lions.

After both combatants were ready, they got into their respective stances. Once they made sure that their protective gear was on correctly, they began sparring. Sword slices were dealt, and each combatant was invested into the fight, but not enough to injure their competitor. Any hits that were inflicted on either Byleth or Celine were deflected by the protective gear worn by the combatants. Celine and Byleth ended the sparring session with both combatants disarming the other. Once they picked up their swords, and Blythe returned to her spot between her brother and Celine, Byleth addressed the rest of the Blue Lions. "That is how a sparring session between two combatants using real weapons should go. The weapons and styles may be different, but the underlying principle is the same. You use the skills that you know in the sparring session. If you must use some amount of force in a sparring session, it should be enough to incapacitate, not kill."

"Before we do individual practice..." Byleth started to say before he looked intently at the Blue Lions. The teal-haired professor continued his statement. “We will do pair sparring. I have already paired you all up, with some adjustments to suit everyone’s needs. The groups are...”

”Celine and Sylvain.” Celine smiled at Sylvain, until he tried to wrap his arm around her shoulders. She ducked out of the way of the Gautier’s arm with a smirk.

”Ingrid and Dedue.” Dedue was indifferent about the pairing, but Byleth could spot a small amount of animosity in Ingrid’s green eyes. If Byleth had to infer, it had to do with something in Ingrid’s past.

”Annette and Ashe.” Both Ashe and Annette gave nervous smiles at each other.

”Blythe and Mercedes.” Mercedes looked down to the ground with downcast eyes. Blythe squeezed Mercedes’s hand reassuringly, and the pinkish-blonde haired woman looked at Blythe with a smile.

"And the last group is Dimitri and Felix." Dimitri gave a light smile to his old friend, but the blue-haired swordsman audibly scoffed in reply while mumbling something under his breath.

”Those who fight with magic or arrows will have a partner who is wearing a leather shield along with the sparring protection.” Byleth told the class. He then turned to his sister, and told her, “Blythe, I want you to focus on your magic for the pair sparring, and your sword for the individual practice.”

Blythe nodded in reply while giving an affirmative noise. She would follow her brother’s instructions. It wouldn’t be fair otherwise.

"I will be supervising this to make sure that you all do not hurt each other." Byleth said, his piercing stare looking at every Blue Lion. "Training weapons don't hurt the combatants, since they are designed that way. Real weapons, on the other hand, have a high possibility of injury if they are not used correctly. I want you all to use your best judgement in this training session."

All of the Blue Lions nodded in unison. They then began their training session, using caution to not injure their classmates.
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18th of the Harpstring Moon, Outside Garreg Mach Monastery, (Early Afternoon), Imperial Year 1180

The Blue Lions were at one end of the clearing, behind the shelter of trees. It was the Blue Lions, Byleth, and all of the men under their command. In order to test the authority of the Blue Lions, Byleth had gotten permission from the archbishop and the battalion guild master to rent out battalions for his students to use. He had rented out the Seiros Mercenaries battalion, along with two of the Church of Seiros soldiers battalions. They would normally only let one type of each battalion be rented out at once, but Byleth was allowed two as a result of his bigger class size. Jeralt also gave Byleth permission to have the mercenary group under his and Blythe's command.

Out of the seventy-five mercenaries in the mercenary group, Byleth had thirty-eight mercenaries under his command, and Blythe had thirty-seven mercenaries under her command. The other Blue Lions split up the three battalions amongst themselves. Celine, Felix, and Sylvain took command of the Church of Seiros Mercenaries, with ten men each. The other six Blue Lions split up the sixty total men for the two Church of Seiros soldiers battalions, with ten men each.

The knights did the same thing amongst themselves, but they were on the other end of the forest. Everyone was using training weapons, and they had to follow the directions given to them by Jeralt and Rhea. Both sides were to use the tactics and teachings of their professor/captain. The knights were also asked to not give it their all in this mock battle, so the students can have a decent chance at victory. They wouldn’t make it easy for the Blue Lions to achieve victory, though.

Jeralt, who as the Captain of the Knights of Seiros, was overseeing the mock battle between the knights and the Blue Lions. He gave the signal for the battle to begin.

Byleth led the Blue Lions into the mock battle against the Knights of Seiros. The men under their command followed behind as well. The Blue Lions split up into three lines; a front, middle, and back line. Byleth, Dimitri, Celine, and Felix were the front line. In the middle line was Ingrid, Sylvain, Dedue, and Ashe. The back line was Mercedes, Annette, and Blythe. Byleth wanted the other Blue Lions to have a chance at leading, so he asked Blythe to guard Mercedes and Annette in case anything went awry. Blythe could see where her brother was coming from, so she accepted the job. In return, though, Blythe wanted to be on the front line during their mission. Seeing no way around it, the teal-haired professor accepted Blythe’s offer.

The teal-haired professor also wanted his class to use the ‘buddy system’ during this mission, and any subsequent ones. Each student would have someone to watch their back, if not more than one person. In the mock battle, Byleth and Dimitri fought together, and so did Celine and Felix. In the middle line, Ingrid fought together with Ashe, and Sylvain did the same with Dedue. All of the back line fought together, with Annette and Mercedes giving Blythe support by using their magic to incapacitate the ranged enemies, while Blythe took care of the close-range enemies with her spells and swordsmanship.

With all of them working together, the Blue Lions were the victors of the mock battle with minimal losses. The only people that the Blue Lions 'lost' were a few members of the battalions that were incapacitated by the Knights of Seiros. Both Byleth and Jeralt looked at each other and nodded. They both thought that each side did well in this mock battle.———————————————————————————————————————————————————

23rd of the Harpstring Moon, Garreg Mach Monastery, Blue Lions Classroom (Afternoon), Imperial Year 1180

After classes were over for the day, Annette, Blythe, and Celine crowded around a table in the Blue Lions classroom. They were talking quietly about something, like they didn't want anyone to know what they were planning. It was cleared up when Annette told Blythe and Celine, "Ooooh! Planning a party is hard!"

"It's not so much hard as it is tricky, Anne." Celine said to Annette while using the nickname that Celine came up with for the orange-haired mage. Blythe nodded in reply to what Celine said. "Celine's right, Annette. Merce is going to like this no matter what we do. It's the thought that counts."

"Even if it's going to be like my party a few weeks ago?" Annette responded while looking back at Blythe and Celine. Both girls nodded in reply.

"If anything, I might ask the Professor if we could do this for every Blue Lion's birthday." Blythe told the two while twirling a piece of her hair.

"That sounds like a good idea." Both Annette and Celine said at the same time. They then looked to each other and smiled.

"So..." Annette started before continuing. "Who's going to have what jobs again? We said it at the beginning, but I don't think I remember them correctly."

"I would be in the kitchen along with the Professor, Dedue, and Ashe making the food. Celine would be in the classroom decorating with Dimitri, Ingrid, Felix, and Sylvain. You would be hanging out with Merce until it's time to come back." Blythe told the orange-haired mage. 

Annette nodded in reply, and the three Blue Lions females continued planning for Mercedes' birthday party in four days, which was the 27th of the Harpstring Moon.
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25th of the Harpstring Moon, Garreg Mach Monastery, Blue Lions Classroom (Late Morning), Imperial Year 1180

Byleth was in the Blue Lions classroom, setting up for the seminar that he is hosting today. The archbishop wanted all of the professors and knights to host a seminar for the students to attend. It was for the students to ‘expand their knowledge on certain subjects’, in the words of the archbishop. Byleth designed his seminar to focus on swordsmanship and authority. Each seminar had a maximum of six students allowed in the seminar, and Byleth’s was one of the first seminars to fill up. When the teal-haired professor looked at his sign up sheet, he was slightly surprised at the names listed.

He had all three house leaders in his seminar for today. Edelgard was the top name on his sign up sheet, so it was obvious that the white-haired Hresvelg wanted to be a part of Byleth’s seminar. Dimitri’s name was signed under Edelgard’s, and Claude’s name was signed under Dimitri’s. Felix was the fourth name on the sign up sheet, with Celine’s name signed underneath of Felix’s. Ingrid was the sixth person to sign, so she was the last student in the seminar.

From what Byleth heard from Dimitri and Celine, Blythe was attending Manuela’s seminar that day. The female professor’s seminar focused on faith magic and swordsmanship, so Byleth could understand why Blythe was attending that seminar.

While Byleth was setting up for the seminar, he heard a pair of footsteps coming into the Blue Lions classroom. Byleth set down the book of tactics in his hand and turned around.

The teal-haired professor saw Edelgard in front of him, with the white-haired young woman holding a book over her chest. The Adrestian princess gave a small smile to Byleth. "Good morning, Professor Byleth."

"Good morning, Edelgard." Byleth nodded to Edelgard in response. He then adjusted how his sword's sheathe was on his hip. After finishing, he said to Edelgard, "You're earlier than the scheduled time."

"There's no particular reason for my earliness. I'm just eager to learn from you, Professor." The white-haired princess responded to Byleth's statement. She put the book in her hand down on the table behind her to signify that that was her seat. Edelgard decided to sit where Blythe and Dimitri normally do during class, which was in the front row to the left of the aisle.

Byleth accepted that response. It was perfectly understandable to be excited for a new lesson or event.

"Though I do have something to ask of you..." Edelgard trailed off. At Byleth's inquisitive look, she continued with, "I've been interested in taking lessons in swordsmanship, but Professor Manuela's style of swordsmanship does not suit me. Would you be willing to teach me about wielding a sword?"

"I would be perfectly willing to, Edelgard." Byleth responded with softened eyes. "Would the Garland Moon be acceptable for your first lesson?"

"It is." Edelgard said in response. She then twirled a piece of her hair. "Thank you...my teacher."

Byleth's eyes widened at the title, but he accepted it nonetheless. Both him and Edelgard continued talking, even as the other students began to enter the classroom.
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27th of the Harpstring Moon, Garreg Mach Monastery, Blue Lions Classroom (Early Evening), Imperial Year 1180

Celine was in the classroom with Dimitri, Sylvain, and Felix. They were decorating the classroom for Mercedes’ birthday party. While decorating the classroom, Celine suddenly had a memory flash before her eyes. Before it overwhelmed her, the blue-haired, female swordsman slid down the ladder and sat down on the closest bench. Once she was on the bench, the memory overwhelmed her.

“Come on, big brother!” A young girl with blue hair and eyes said to an older figure behind her. Celine recognized the young girl to be her younger self.

”I’m coming, CeCe.” The older figure responded while chuckling at his little sister’s exuberance. Little Celine giggled in response to her big brother. The little girl threw her hands up in the air. “You said you were teaching me magic! The type of magic you have! How can I slow down? I’m EXCITED!”

”Now, CeCe...” The older figure started while kneeling down in front of his little sister. At her brother’s serious tone, the young girl tilted her head. Trying not to laugh at his sister’s adorableness, Celine’s older brother told the young girl, “Magic can sometimes be dangerous...are you sure that you want to learn it?”

Little Celine nodded furiously while puffing out her cheeks. “Of course I do! I want to protect everyone! Even you, Papa, Mama, and little brother!”

The older figure stood up. He then ruffled Celine’s hair with a smile. “Good girl...Come on, I’ll take you to where Father and Mother taught me magic!”

”YAY!” Little Celine yelled while she jumped on her older brother’s back. The older brother put his arms under Celine’s legs, and gave her a piggyback ride. Celine had a smile the whole time.

The memory gradually faded away from Celine’s focus. She faintly felt someone shaking her shoulder with concern. Wiping the tear that she just noticed was there, Celine looked up to see Sylvain giving her concerned eyes. “Sylvain?”

”You okay?” Sylvain asked while sitting on the bench beside Celine. The blue-haired swordsman nodded in reply. “Yeah, I’m fine. Just got a memory back.”

”At least you’re getting parts of your old life back.” Sylvain said while standing up. Celine was fine, so the red-haired Gautier’s concern was fading away. Celine nodded in reply while also standing up.

The two walked over to Felix and Dimitri, who both had just leaned the ladders they were using on the wall. All four of them looked at their handiwork, and nodded in praise. Celine glanced at Felix, and had a brief thought. She shook her head quickly to rid herself of the thought. It was impossible, right?

Celine was snapped out of her reverie when she heard Blythe and Byleth talking. It seemed like the group from the kitchen had returned. The blue-haired swordsman heard Blythe ask Byleth if each of the Blue Lion birthdays could be held in the Blue Lions classroom, and the teal-haired, blue-eyed professor gave the affirmative.

The four Blue Lions in the classroom then saw the kitchen group come into the classroom. Byleth had a Pheasant Roast with Berry Sauce in his hand, while Blythe had a container of peach sorbet in her hands. Dedue and Ashe had Mercedes' presents in their hands. All four of them placed what they were holding down on the table.

Blythe and Celine looked at each other and smiled. When they heard Mercedes and Annette talking in the distance, they told the others to hide.

Blythe, Celine, and Dimitri hid by the benches. Sylvain, Felix, and Ingrid did the same thing but on the other side. Dedue actually found a place to not be seen, and he was followed there by Ashe and Byleth.

Once Mercedes and Annette arrived, everyone burst out of their hiding spots. The Blue Lions then celebrated Mercedes' party, which was a brief respite from the tension of the upcoming mission.———————————————————————————————————————————————————

Chapter complete!

This chapter had a few scenes inspired from the game, but the rest were original. If you noticed the date of the last scene, it is almost the end of the Harpstring Moon.

Next chapter will be the Zanado mission!

What did you all think of this chapter? I dropped some small hints on Celine's origins near the end of the chapter.

See you next chapter! We will be at Zanado, the Red Canyon!

-YugiohChick