(This was going to be the one shot at the end, but the chance I will completely finish this story is very low, so here it is now.)

[Taken place a few days or weeks after saving Eri and before the Festival. Eri was the white haired girl who's hair resembled Mira's. YN finds their way back to Fairytail]

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Class 1A was finally adjusting to life without one of their dearest friends. The classroom felt quieter now, your snarky comments and loud outbursts gone.
But what could they do about it?
You were back with your family, back where you were supposed to be. You belonged in your world, and the time you spent here must have been torturous, having to worry constantly about your own world. The fear, confusion and alienation you must have felt arriving into their world...

When Aizawa and Nezu came to take your table and chair away, majority of the class clung to it's legs, bawling and begging for it to be left alone. Tsuyu and Jiro had their quirks wrapped around the table and chair, Mina and Denki were clinging onto it, in hysterics. Even Mineta had used his quirk to stick the table onto the ground. 

Others, like Momo and Deku stood with their palm on the table before the teachers, hiccuping reasons for the table to stay and rubbing their teary eyes. Shoji stood to the side, comforting a sobbing Koda.

The rest were sitting at their tables, refusing to act on the scene behind them. Iida and Todoroki saw reason behind their teachers actions, YN won't be back to continue their education, or back at all. There was no need for YN's table anymore.  But seeing your table be taken away would hurt them in an indescribable way. They could not imagine simply erasing the evidence of your existence in the classroom and continuing school life as if you were never there. 

Bakugou stayed in his seat the entire time, refusing to even acknowledge the situation.

Soon enough, the teachers gave up and left your table alone. 
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"She's not dead you know." Aizawa stated once. "Just in another world."

Some students argued that being in heaven an in another world were basically the same concept.

"In the hero world, colleagues may suddenly end up missing or dead. This is the life of a pro hero." 

To him personally, knowing a friend was safe in another world was better than knowing them dead.
Kurogiri...
But Aizawa would agree this situation was upsetting.

"If it makes you lot feel better, they're back at home."

People would think to themselves, No! YN's at home with us! This was YN's home!
But this wasn't  YN's home. They were at home with YN.
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Bakugou, the one who should be the one missing you the most, seemed to be indifferent. Aside from training harder and fighting more violently, he didn't seem to care.

Surprisingly, Bakugou adapted to you being gone quickly. Sure, he did miss your annoying voice and antics at times, but he was fine with the fact that you were back where you belonged. He was the one that was around you the most, spent time with you the most and understood you the most due to the prolonged time you spent living at his house. 

He knew you were alright. Alright and happy. Spending time catching up with your real  family. Bakugou was fine with that. He was. He could cope. He could. Really. 
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It was a few days after rescuing the girl with wavy white hair named Eri when you... when you went back to your home.

In the middle of class, when you were messing around with your friends and annoying All Might when a sudden FLASH BANG! happened. The classroom immediately silenced, quirks at the ready, the USJ incident ingrained into their reflexes. All Might switched from exasperated teacher mode into hero mode immediately. 

"WHO ARE YOU? IF YOU COME WITH ILL INTENT TOWARDS MY STUDENTS OR I, YOU WILL NOT MAKE IT OUT OF THIS ROOM UNSCATHED."

"This dude's in a completely different art style!" A man's voice chuckled. When the white smoke faded into nothing, a beautiful lady in armor stood  in front of a pink haired man and a shirtless one in the middle of the room. 

"Yo Natsu. We're in a school. How 'bout you take this chance to learn how to count?" 
"Oh yeah? How 'bout you put your friggen shirt on, Ice bastard!"

The red haired lady scanned the room and outstretched her hand toward YN. 

"YN LN. It's time to go back home."

Just as All Might was about to attack who he thought were villains who were trying to take one of his students again, you launched yourself into her arms. 

"Erza! Erza! You're here! I know I said I had to stay to fix something in this world but I think I've finished!"  You sniffled, eyes glossy. "I've made so many friends here, but I've missed you guys so much!" 

The lady's expression softened and returned the hug. "Good to know you're growing up, YN."

"BUT YOU COULD HAVE EXPLAINED YOUR SITUATION BETTER!" With a flip of her arm, you were thrown to the ground, cracking it. 

"Blegh." You spat out a bit of blood. "But Errrzaaaa!" 

"No buts." She gave you the her signature glare™. "Do you know how worried we were? Not knowing what universe you ended up in either!"

What in the world was this woman talking about? The class wondered. 

"Sorry guys, I didn't mean to make you all worry." You scrambled up to hug them all. 

Erza turned to All Might. "Apologies for interrupting your class session. I assume you are the teacher of this class?"

All Might, taken aback by the sheer power in the woman's eyes, stuttered "Y-yes. Who are you and what do you mean by universe?"

When it came to YN, All Might had no idea. On what her quirk was, where she came from, her background, on all sorts of things.

"Ah. I understand your confusion. Three strangers burst into your classroom with magic and demand to take one of your students away-"

"Magic? You mean quirks?"

"-whatever your power system is called, I suppose. I have time to explain majority of your questions, Gray pass me the paper I wrote on."

"..." Gray put his hand on his chest, his eyes widening. "It was in my pocket, I swear!"

"Your shirt pocket, that is." Natsu sniggered. "That's what you get for being a stripper, ice princess."

"Shut UP, Ash brain!" Gray's swung his fist at the pink haired boy, but that hit never made contact. 

Erza's hit did though.
In a split second, both Natsu and Gray were slumped across the room. 

"I apologize for their indecency. We come from the world called Earthland. In Earthland, some people learn how to wield magic. These people are called mages. Mages who wish to use their magic to earn money and save people join places called guilds, where job requests and missions are sent to. We choose from the variety of jobs available and help the client with our magic. YN here, is part of the number one guild Fairy Tail." 

Natsu and Gray had returned to their places beside Erza. 

"Yeah! We're number one in the whole of Fiore!" Natsu lit up his fist and punched the air.

"If you're worried about if we're talking the truth you could just check out our guild marks." Gray shrugged, noticing the skeptical expression of All Might.

Natsu flexed his arm, making the red fairy bulge. Gray puffed up his chest in pride to show his blue fairy tattoo and Erza pointed to her arm.

"The family crest?" Momo gasped, and all the girls eyes flew to YN's arm, remembering what YN told them in the changing rooms. The boys however, were confused. 

"What mark, YN?" Midoriya asked.

"WHY DIDN'T YOU TELL ME YOU WERE FROM ANOTHER WORLD? YOU FAIRY BASTARD!" Bakugou was fuming that you kept such a large secret from him.

"Ahh..." Scratching your head, you answered, "Well, I didn't think you would believe me? I mean, half the class still doesn't believe Erza right now." Shrugging off your UA jacket, you rolled up the white shirt sleeve. Showing your fairy mark to the world. 

"Sorry, guys. I would have probably been outcasted to weird scientists if everyone knew about where I came from. And I wanted to fit in too."

"Wait." Mina looked horrified. "Does that mean you'll have to leave our world?"

"Yeah, I suppose-"

"YOU'RE NOT TAKING HER!" An explosion headed straight for Erza. "HOW DO WE KNOW IF YOU WARPED HER MEMORY OR SOME SHIT?! YOU CAN'T JUST BARGE IN AND SAY YOU'RE TAKING HER TO ANOTHER WORLD!" Bakugou growled. "MAGIC? GIMME A BREAK! HOW BELIEVABLE IS THAT?" He launched straight for her.

"RE-EQUIP! FLAME EMPRESS ARMOUR!" A golden flash enveloped Erza's body, and her armor had changed. BOOM! 

"Bakugou!" Everyone screamed. Attacking someone from another world? Without knowing how strong they were? 

When the dust from the explosion settled, Bakugou was pinned to the wall with the length of a red sword at his throat. He swallowed and grinded his teeth angrily. 

"Erza! Don't hurt him!" YN cried out. "Bakugou's like Natsu's angry mode, just twenty four seven!"

Erza looked at you, and her sword lingered for a few seconds before she dropped her arm. Bakugou slumped into his seat, shadows covering his eyes.  

"I see." Erza paused. "I cannot prove to you that we are not influencing YN with spells, but would this picture ease your concerns a little?"  A flash of gold left a piece of paper in her hands. She handed it to Bakugou. 

He snatched the picture roughly and scratched at it. Handing it back he mumbled "Yeah."

It was a printed picture of you and and the guild from a few years back, when you all were really young. 

You looked at him sadly. "Sorry Katsuki. I really didn't know how to tell you." 

"Yeah, whatever." He didn't look up at you.

"YN!" Hagakure gasped. "You're arms are fading!"

Looking down, your arms were indeed, turning into gold dust. 

"YOUNG LN! WE HAVEN'T CONFIRMED IF THESE PEOPLE ARE SAFE YET!" All Might tried to grab your arm, but his hand passed right through. 

"Sorry everyone, but this is my body turning back into etherano. I'll try visit! I'll tell everyone back at home about technology and you guys! I'll miss you! I love you guys! Next time, I'll take you-" Your mouth dissolved into gold dust and the rest of your head followed quickly after. 

The people who had tried to hug you one last time crashed into each other, and All Might looked on with a gaping mouth. 

"Alright class, I'll go talk to Aizawa and Nezu about this." All Might hurried out of the room. How was he going to explain this to them?
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Surprisingly, Principal Nezu believed him almost immediately.  "Another world you say?" He had stated. "There was no way Earth was the only planet with civilization out there. Considering which student we're talking about, I suppose that this situation isn't quite unbelievable."

Aizawa, had stated in the meeting, "LN YN is a strange person. The people who took her could have been someone using their quirks to trick us and take our student. If it were any other student, I would have sued you for losing a student in your own classroom, but regarding the magic matter, I couldn't erase her visibly emitter quirk."

"I see, I see." All Might frowned. "So we're just going to let her go?"

"I suppose," said Nezu. "Bakugou still has that picture, does he not?"

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When Bakugou went home, he had slammed the door and immediately gone to his room. Few hours later, when his mother and father went upstairs to inquire where YN had went, he had replied, "Gone to a different world." 

This had obviously sparked misunderstanding, and Mitsuki thought that you were dead. Thus began an angry explanation from Bakugou, which ended with him showing his parents the photo. 

"Katsuki, it's alright to be sad you know?" His father told him softly. 

"I'M NOT FUCKING SAD, GODDAMNIT! LEAVE ME ALONE!" 

His parents left the room, silently, surprisingly.

"We knew that girl wasn't ours from the start, but..." Mitsuki's voice wavered, softly. "...why does it feel like I just lost my child?" 

"It's okay, darling." Masaru muttered. "I understand you, we all do." 

The Bakugou household all went to bed earlier than normal that day.
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Things that reminded everyone of you littered the table.

You were back where you belonged.

Despite knowing this... was it selfish, wanting you back? Was it selfish to wish that-

"AaaaAAAAAAAAAAGGGRGGGGGHHHHHhhhhhhh!!!"  A scream could be heard, descending from the heavens. It soon abruptly stopped with a dull thudding sound.  

"SHIT I GOT THE COORDINATES WRONG!" 

Aizawa and All Might paused the lesson and stared at the wall. Was it another villian?

"Class, settle down. We'll go check what it is."

BOOM!

"No need to sensei! It's just me! And there's going to be a change in your lesson plan everyone!"

"YN!!!!" Everyone jumped from their seats to hug you. Its been months. "YOU'RE BACK!"

"LN YN, you better be paying for that wall." Aizawa glared.

"Y-yes sensei!"

"Also, changing lesson plans is irrational-"

"Too late sensei, particle teleportation has already been set to certain individuals for a certain set time!"

"And that time is?"

"NOW!"

A purple magic circle that's diameter covered the room appeared and everyone's arms started fading into golden dust. 

"ARE WE VISITING YOUR WORLD?!" 

"YEAH!"

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Bakugou residence

"MASARU! MASARU! WHAT THE FUCK IS THAT PURPLE CIRCLE UNDER ME??"

"I DON'T KNOW HONEY! HELP, I'M TURNING INTO GOLD DUST!"

"THIS HAS TO BE DAMNED KATSUKI'S FAULT!"
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UA Principles office

"Oh? What a pretty purple circle. Almost looks other worldly."
"..."
"Ah, I'm turning into gold dust. Guess I was correct then."
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UA Staff Break Room

"Mirio! Mirio! I'm turning into gold dust! And there's a purple circle under me!"

"Eri, come here!"

"Are you okay, kids?! What's this circle?!"
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[1A and others on their way to therapy!]