Disclaimer: I do not own any character mentioned here or the anime/manga/game they belong to. Also, massive crossover warning apply!

Now, insert Unravel (Tokyo Ghoul) as opening theme.

[-x-x-x-]

Inside the insanely large amphitheatre classroom, several confused individuals were around, wondering what just happened. While most of them did not look anywhere like students, they certainly were anxious about what was happening.

"What the hell is going on?" A blonde girl clad in a tub top and baggy pants roared as she recognized no one.

~ Leone (Akame ga Kill) ~

"The hell are you?" The girl standing beside her yelled back. She had long silver hair attached in a ponytail and had a deep scar running her face. Being clad in a school uniform, one could dedict she would be around 15 to 18.

~ Banba Shin'ya (Akuma no Riddle) ~

"Wait. Let's calm down, everyone." An individual clad in a medieval armor got in between the two. The person had a childish face and long pink hair attached in French braids.

~ Astolfo (Fate/Apocrypha) ~

While these three were gathered there, several people just watched, not wanting to get involved in the trouble. Among them was a girl with very long raven hair and clad in an orange priestess outfit. She frowned, confused. "What is this place?"

~ Himemiya Chikane (Kannazuki no Miko) ~

Beside her stood a meek girl with shord red hair and clad in a short red dress. She seemed at total unease since there were no one she recognized around.

~ Izetta (Shuumatsu no Izetta) ~

"This is insane." A slime standing atop a large table commented to no one in particular. "Did I get teleported into another world again?"

~ Rimuru Tempest (Tensei Shitara Slime Datta Ken) ~

"Oh my~" A young girl whose hair was attached in twintails turned to the slime. It was not the first time she was sent into another world and despite being scared, she knew there was no need to panic. "So cute~"

~ Wendy Marvel (Fairy Tail) ~

At the corner of the room though stood several other individuals, less social but certainly as confused as everyone. "Hmmm..." The individual clad in a full armor from head to hells folded their arms.

~ Goblin Slayer (Goblin Slayer) ~

There was also a young boy wearing a baggy school uniform who had very little presence and hid in the shadow waiting. "Let us wait for now..."

~ Shiota Nagisa (Assassination Classroom) ~

As everyone else seemed worried, one person seemed calm though. He was already trapped in a game before so he just needed to wait and solve the puzzle this time. The boy was wearing a long black coat and a sword rested on his belt.

~ Kirigaya Kazuto/Kirito (Sword Art Online) ~

Beside him stood a rather short individual wearing what seemed like a medieval suit and a green cape. He had some weird mechanical devices to stock the blades of his swords. "The hell is this filthy place?"

~ Levi Ackerman (Shingeki no Kyojin) ~

"W-what do I do?" A girl who seemed completely normal among the mass panicked, yet stunned in place. She was clad in a tracksuit, her short brown hair covering one eye. "Hinata... save me..."

~ Hoshino Miyako (Watashi ni Tenshi ga Maiorita) ~

Near the blackboard, a boy wearing a black school uniform with tight collar waited. He had short raven hair while his eyes are red and the motif of a bird on them. "It looks like everyone here is weird. One thing is sure, this is not the world I know. Better be careful."

~ Lelouche vi Britania (Code Geass) ~

The last individual in the class was unlike everyone as she quietly sat on the front row. She was not human is one judged the pair of black wings on her back. She could just look normal though with the medieval style dress and short dark hair attached in buns.

~ Myrrh (Fire Emblem) ~

"Sorry for the wait!" After what seemed like an eternity, the door to the classroom finally opened. Weirdly enough, said doors and windows were all locked but open up all at once as a handsome man wearing a complete suit walked in. He was rather intimidating with the short blue hair and his way of walking.

"Who the hell are you?" Leone and Shin'ya yelled at once, approaching the man. Before they could do anything, a very dark aura stunned them.

The teacher stopped in front of his dest and glared at everyone. Said people shivered at the threatening danger, even Kirito. "I am Amai Mask and will be one of your teacher."

~ Amai Mask (One Punch Man) ~

"Pray explain yourself." Lelouche asked discreetly, trying to keep his calm facade as to not seem weak, yet not provocating the man calling himself Amai Mask.

"You people were summoned on this world for one reason." A very intimidating man walked in. He was clad in a suit and his long black hair was cut past ears. What stood up the most were his pair of black feather wings and horns atop the head.

~ Kazama Jin (Tekken) ~

"Have you already heard about the war between worlds?"

"What do you mean?" Goblin Slayer asked, unfolding his arms.

"Actually, this world is composed of thousands of parallel universe called the Anime Multiverse-"

"What a lame name." Shin'ya commented mentally before letting go of a sigh and listed to what Jin had to say.

"Some of the dimensions has recently discovered a way to move into another dimense. That phenomena is called isekai. Recently, a group of powerful being has been gathered in another parallel universe and they plan on taking every single world one. From now on, you people will be trained by us so you can defend your world and the people you care about."

Silence filled the room for a moment before Miyako raised a hand very reluctantly. "Why me...? I mean I have no special power so why am I here?"

"You do have." Another person entered the room. This one was a woman clad in a house dress, her long red hair let down. Like the other teachers, she also had a dark aura around her. "Some of you might not have noticed but you all have insane potential. Some of you were limited by your dimension's rule or someone else. We are going to teach you how to control your power though."

~ Uzumaki Kushina (Naruto) ~

"And why should we listen to you?" Leone asked.

Astolfo wanted to stop her but he was also curious about the whole situation. He didn't feel like he was summoned this time because there seemed no link with anyone present on the room.

"We have no reason to lie to you all." The red-head explained. "I was astonished myself when a group of people has approached me and explained the situation. It might be hard to accept at first but I pray of you all to keep your calm for now. We will explain everything slowly but surely so everyone understand."

There was another moment of silence before Lelouche sighed and walked toward the front table. "Fine then! I guess I can lend a ear." He commented. 'Since there is nothing left I could do on my world as I left everything to Suzaku.'

The others were a little reluctant but little by little took seat. As everyone took place, one last individual stepped into the room. This one had spiky black hair and was wearing a chinese orange outfit. "Sorry for the wait!"

~ San Goku (Dragon Ball) ~

"I overslept. My bad." He apologized, making everyone else to sweatdrop. The man just cleared his throat and stood in front of the blackboard, facing the newcomers. "First of all, I must thank you all for your cooperation and calmness. Long story short, I am the chairman of this school, Goku. Recently, several worlds has been destroyed by godlike powerful human beings so this is our way of counterattack. I know it sound weird but I beg of you all to cooperate so we can survive this crisis."

With that, he gave a polite bow and stepped back, allowing the only woman teacher to take the relay. "Since it is our first time meeting and since we are going to be together for a while, let us get along well and introduce each others. My name is Uzumaki Kushina and I am a Kunoichi."

"Kunoichi?" The unfamiliar people with the term woundered but decided to not pray too much into it.

"I am Kazama Jin!" The intimidating teacher just said calmly. "Count on me to train you all hard so you won't die meaninglessly on the battlefield."

Miyako shivered at these words. "Man! I want to go home..."

"As I said earlier," this time was the blue-haired teacher's turn. "I am Amai Mask and I will be your main teacher. Cowards wil not be tolerated and punished severely."

With the teacher's presentation done, everyone was aware the different of strength is too much. Doing anything reckless would be bad so they went with the flow. The girl sitting on the first row with repunzer hair was the first to stand up. "I am Himemiya Chikane, a Miko."

"There is no need to hide anything. The reason most of you are here is because you did something awful in your world and need to atone for these sins." Jin commented. "Sharing them might not be bad as to build a relation of confidence."

Chikane sighed. She didn't want to say anything that could put her privacy in danger but some force kept pressuring her mind, as if someone was mentally provocating her. After a good moment of thinking, she decided to say part of truth but not everything. "I hurt the people I liked so they would hate me as to save the world. In the end, I felt lonely and want to find them again."

"That's such a honest answer~" Kushina praised the girl who sat down. "Everyone, please do like Himemiya-san did and reveal everything weighting your heart. Everyone here has something in common; a painful past, so I am sure we can get along well."

At these words, the Manakete nodded and stood up. Everyone's attention turned to her as it was not everyday that they got to meed a dracogirl. "I am Myrrh. Truth is my name is longer but since the humans couldn't speak it, it became forgotten. On my continent named Magvel, there are races of people known as Manakete able to transform into dragon and I am the last of them. My sin is not being able to save the other Manakete."

After that, she sat back down in silence. The other people felt sad for her but the Lelouche decided to stand up. "I am Lelouche vi Britania, a student. My world was ravaged by war, my folk enslaved and tortured. Few months ago though, a group of juice's ally has risen to save the people. My only regret is not being able to see my sister's smile again."

"Poor thing..." Leone commented before standing up. She was on the second row so it was normal her turn came. "Now, about me; I am Leone and as long as you don't do stupid shits, we can get along well."

"Language!" Kushina gave a threatening aura, sending cold chills down the blonde's throat.

The imperial arm user gulped and decided to continue. "My world was ruled by corruption and inequality so a group of people stood to kill the manipulative bastards. In the end, I was wounded badly and lost my imperial arm before having the occasion to declare my flame to the girl I like." At that, the image of a girl with long raven hair and crimson irises flashed in her mind. "That's all!"

Some of the people around were confused by her last sentence. For people from advanced world, same-sex relationship was nothing new but some others were still flustered like the young Sky Dragon Slayer, whose turn has come.

"M-my name is Wendy Marvel and I am a Sky Dragon Slayer. I am also member of a mage guild named Fairy Tail on the Kingdom of Fiore." She said, her mind turning dizzy, not used to so many people looking at her at once. "E-eh... T-thuth is... recently, an undead wizard has attacked our hometown and killed lot of people. My biggest regret was to not be able to save Chelia who sacrificed herself for my sake."

She then sat down, her eyes empty and ready to pass away any time. The blonde beside her patted her head. "Are you okay, Wendy?"

The girl just nodded weakly. "Sorry for that. I am not used to speaking in front that many people. Also, I am still confused about these worlds stuff."

"You're still young so you shouldn't think too much about complex things. Even though that dude is suspicious." Leone pointed at Amai Mask. "One thing is sure, no way in hell I am letting you die without doing anything. You know, I have a thing for kids after all."

Wendy blushed madly at that, especially as Leone pressed the poor girl's face in between her cleavage. Some of the other students sweatdropped while others felt pity.

"All right! I will go next then." Astolfo was the next to go. "I an Astolfo and I used to be a Paladin serving under the King of Francs. There aren't that many interesting things I could say beside let us get along well. Since everyone here seems like good people, I am sure there should be no problem."

The red-head teacher applauded at that. "Thank you, Astolfo-san!"

As the Knight sat down, the one sitting beside him stood up. "I am Shiota Nagisa, a common student. One year ago, a creature calling himself an alien has started being our teacher and changed our lives. I owe everything to him and wish to fight for my own justice."

As the boy sat down, the girl behind him stood up loudly. "Gotta admit it's not everyday that I get to see the sun!" She laughed loudly, everyone turning to her. "I am Banba Shin'ya and my only raison d'être is to protect my alternate self Mahiru from harm. Also, I am an assassin but I do not kill for fun or anything... just to pritect Mahiru, even if it means accepting the situation."

The room became quiet after that before the slime behind Shin'ya decided to take action. "E-eh... I am Rimuru Tempest, a slime. Recently, I have managed to build a nation for monsters with the help of goblins-"

The slime shivered though after saying that as a pair of bright red eyes fixed at him with rage. "That sound interesting." Goblin Slayer who sate at the other side of the room but in the same row commented. "I will need to find them."

Rimure sweatdropped. "A-anyway, I hope we could get along well!"

With the slime's turn over, the armor-clad man stood up. "You can call me Goblin Slayer because I slay goblins. These disgusting things are no idiot but not genius either. They can reproduce very fast and can be an annoyance as they see in the dark and can adapt easily. Also-"

"I guess that's enough info about goblin." Kushina cut him. "How about you tell us something about you insteat."

The man paused before giving a quick answer. "I have no interest in anything except slaying goblin. That's all!"

Everyone else felt awkward at that. It was now Kazuto's turn to say something and he hoped he would be able to brush the awkwardness away. "I an Kirito, a college student. Recently, my friends and I were trapped in a video game and went through hell. I do not want to lose anyone dear to me so I hope we could defeat the evil guys and bring back peace on the Anime Miltiverse."

The presentation went well,even earlier a nice ovation. Thanks to that, some of the students felt more comfortable. At least, some...but certainly not a certain meek costume designer. "Do I really have to do this...?" Miyako reluctantly stood up. "H-Hoshino Miyako."

"Sorry, could you speak a little louder?" Goku asked politely.

"H-Hoshino Miyako... college student... that's all..." And with that, she sat back down.

The others were unsure, especially Izetta who sat beside her. She reluctantly stood up. "M-my name is Izetta and I am a witch at the service of the Princess Otfiné von Frederick from the kingdom of Eilsdadt. For the Princess' sake, I took arms and fought for what was precious to her. Even now, I want to do my best to protect the peace the Princess Finé has managed to build. P-please let's get along well!" She gave a bow, her eyes shut.

"Oh my. That so gay!" Shin'ya yelled and the witch went beet red, sitting back down.

"G-gay...?" Myrrh wonder. "What does that mean?" She turned to the Miko.

"You are too young for that." Chikane just responded, hiding her blushing face.

"Why...?" The Manakete then turned to the young Britania who also seemed flustered.

"Let us stop about that talk for now. You are too young to understand."

Myrrh puffed her cheeks childishly. "Compared to most humans, I am ten times older so why does everyone keep treating me like a kid?"

Nagisa just chuckled awkwardly until Levi decided to go next. He didn't even mind standing up, arms folded. "I am Levi. Just Levi. I am from a world where filthy giants are eating humans and the bastards at the hierarchy keeps doing shit. Seeing that there are other brats outside of the walls is something I didn't expect to be honest."

"I guess that's all." Goku clapped his hands. "Let us get along well and start training tomorrow! For now, you will be assigned to the dorms, the other building facing this one." He pointed to the window and there really was a fancy building there. "The dorm assignment would be a room for a person but we won't stop you from sharing a room or something."

At that, Leone got a whicked idea. "Hey, Wendy and Myrrh. How about we three share a room? I promise I will not to anything immoral during your sleep."

"Just you saying that is making it sound suspicious." Lelouche sighed before standing up and left the classroom. Soon enough, everyone followed, either tired and wanting to take a rest at the dorm or hanging around and inspect what they could.

"What am I going to do now...?" One introvert girl started to cry. "Hinata! Hana-chan! Noa-chan!"

"Are you okay?" A hand on her shoulder brought the girl back on her mind and watched Chikane trying to comfort her. "It might not be of a huge help but please accept this handkerchief."

Miyako sobbed and accepted the offer. "Thank you..."

Chikane just smiled. "Pay no mind to it. I just want to help as much as I could... all for that one person's sake." She then looked up at the high ceiling, her mind wandering. "Himeko... no matter what, I will protect the world you cherish so much."

[-x-x-x-]

A/N: World-building is a pain but I have no regret. Now, insert "Gurenge" by LiSA (Kimetsu no Yaiba) as ending theme.