Just a list of what series will be in here:

Jitsu wa Watashi wa, Is This a Zombie?, Haiyore! Nyaruko-san, Shakugan no Shana, Date A Live, and My Teen Romantic Comedy SNAFU. There are also quite a lot of references to other anime, so look out.

Alright let's get to it

Chapter 1: The Different Universes

The truth...

For all his life, Asahi Kuromine couldn't keep it from others. He couldn't lie. If he tried to tell one, his facial expressions would give it away.

Thus, he was given the nickname of "Holey Sieve".

However, for an entire year now, he had been keeping the world's deepest secret. A secret deeper than anything any government could hold.

Monsters existed and walked alongside man.

Soon enough, though, keeping quiet about a few bloodsuckers were going to be the least of his problems.

...

"Hey, Asahi."

"Asahi, over here!"

"Good morning, Asahi!"

Asahi grinned as he saw his three best friends Oka, Shima, and Sakurada on his way to school. He jogged over to catch up to them.

"Hey, guys! Good morning!" he greeted them back.

Shima grabbed Asahi in a headlock and said, "So, Asahi, how are you and Shiragami doing these days?"

Asahi chuckled, feeling a bit embarrassed, and responded, "Well, we haven't done anything too over the top..."

"Who said anything about what you two are doing?" Oka questioned, one eyebrow raised.

"...well crap."

They all burst out laughing.

Funny. All three of them were supposed to be the tightest of friends out there, yet Asahi had been keeping so many secrets from them. And they thought he was telling them the whole truth due to his reputation. For better or worse, he learned to lie. Even if he kept these lies from his own best friends.

Truth be told, it hurt to keep them in the dark about the bare truth of the world.

As they continued their horseplay on their way to school, Asahi heard Sakurada say, "Hey, that isn't our school uniform, is it?"

Asahi, Shima, and Oka followed Sakurada's gaze. Indeed, there was a boy walking in the same direction as them from the other side of the street wearing an open black jacket with a school crest over his heart with a button up white shirt underneath it.

Weird.

"Maybe he's lost?" Shima suggested.

Clearly not. The guy didn't look at all nervous and was walking with purpose in his stride.

The four friends traded looks as they approached the school's front gates, expecting the other student to see that this was not his school and turn back. This was not the case, however, as... well...

"How can so many people be lost?" Oka muttered.

There was a multitude of students roaming the schoolyard, wearing varying uniforms that weren't matching their own. Besides their own, Asahi could pick out at least four different uniforms.

His head spinning from confusion, Asahi asked, "Are we at the wrong school?"

"Nope, this is definitely our place. Same route as everyday," Shima confirmed.

"Let's just go inside and let things sort themselves out," Sakurada offered.

With a silent agreement, the four began to walk into their classroom.

"Hey, Asahi," Oka suddenly asked. "Where's Shiragami?"

Asahi sighed and responded, "She's sick at home, so I'm gonna bring her homework to her later."

Sakura opened the door to the classroom and-

"What the hell makes kinako bread so good?! It's not all that sweet!"

"Yeah?! Well... uh... melon bread tastes bad!"

"Oh, you did not just go there!"

Wearing two different uniforms was a short, black haired girl and a taller, shapely purple haired girl. The shorter one was insulting kinako bread, fuming angrily all the while, as the taller girl poorly argued against melon bread.

"Hey, Shana..." a brown haired boy pleaded, but neither girl responded to him.

Everybody leaped in surprise as one of the door slammed open a bit too hard. Komouto-sensei stomped into the room, looking a bit like she was suffering from a hangover.

"Alright everybody," she growled, her tired voice carrying a heavy threat behind it. "Sit down and shut up!"

There was confusion as the students in the room tried to figure out where to sit. Asahi, luckily, managed to get his usual seat. He noticed Aizawa Nagisa argue over a seat with a silver-haired girl with a long ahoge, and won it after a few seconds, letting the unnamed girl walk away, sulking. Shima, Oka, and Sakurada's usual seats were already taken so they had to pick out random spots.

Eventually, every seat was taken. Asahi immediately thought, Wait, what about Youko?

"Well crap, it seems I need to make a new seating chart," Komouto-sensei muttered. "So anyways, I hope you are not too confused. We're having some confusion with the schools that we're gonna fix eventually."

Dozens of questions were thrown into the air at once, and a vein throbbed in Komouto-sensei's head.

"Shut up!" she shouted. "We're trying to fix things, alright?! We don't know how long it'll take, but we're trying, alright?! Now clam it!"

Everybody eventually settled down, but it didn't stop the confusion going around in Asahi's head. Why were the schools all mixed up like this? How could they be so disarrayed?

After that, Komouto-sensei went on with her day like usual, and Asahi tried not to notice the difference.

...

Shaking her head sadly, Mikan sighed and said, "I'm not even gonna go all Heathen Queen right now when I say this: I have no idea what messed things up this badly."

Asahi felt a chill go down his side. If Mikan didn't know, then that means nobody did. Still feeling he had to try, he turned to Rin who was right at Mikan's side and asked, "You neither, Rin-chan?"

Rin's face fell as she said meekly, "Sorry, Asahi. The time machine doesn't let me see anything from between this morning and last night."

Asahi's brow furrowed in confusion.

"Asahi Kuromine, please come to the principal's office immediately," a voice said over the loudspeaker.

Mikan's solemn frown changed to her Heathen Queen smirk as she teased, "Oooh, whadya do this time, Asahi?"

"Shut up, Mikan!" Asahi shouted, annoyed.

Mikan's giggle infuriated Asahi as he went to visit the Devil.

...

On his way up, Asahi noticed that there were five other calls to the principal's office. The names were unfamiliar to him, but he did manage to catch each of them: "Mahiro Yasaka", "Shido Itsuka", "Yuji Sakai", "Ayumu Aikawa", and "Hachiman Hikigaya". All five of them, whoever they were, had already arrived at the principal's office, and with a jolt of realization Asahi realized that they were all in his new mixed-up homeroom class. After a quick scan, he wasn't able to label faces to names, but he was able to pick out that one was absurdly normal-looking and had a fork in his hand, another had the sleazy look of a lazy person, and then another who was further away from everybody had the eyes of... dead fish? There was also the brown-haired guy from before, which, upon closer inspection, Asahi noted was kinda tanned and had pretty messy hair.

Akane Komouto, the principal sat at her desk, looking about twelve years old as usual. The pink haired, horned girl usual had a grin on her face that said she was ready to mess up someone's life and had a pile of candy in front of her, but today she looked dead serious and had her candy dumped into a corner.

The fact that Komouto-sensei (her great-granddaughter) was not in the room implied that this was all Akane. Something about that sent a shiver down Asahi's spine.

Akane considered them all and took a deep breath before finally saying, "So, how about you all sit down and get to know each other?"

They all stared at her, know she expected more.

"And tell the whole truth. Like this: 'Hi! I'm Akane Komouto, the centuries-old devil who is now your principal!'"

Asahi, his mind spinning because of her seriousness, asked her: "Principal, did you get hit in the head today?"

Akane shook her head and said, "This is a serious matter, Kuromine. I can't figure out what's going here myself, and it has brought more than just monsters to this school. Now go on. Get to know each other to see what you're now dealing with."

...

"My name's Asahi Kuromine. I had to keep a secret about how this school had monsters attending the school like regular students. And they're all stupid."

The others nodded with sympathy. His story wasn't too long. Just keeping it simple.

One guy, a blue haired one, went next. Then the plain guy, sleazy one, and then the fairly tanned guy with messy hair.

The blue-haired guy, who was named Shido Itsuka, had to deal with 'Spirits', girls who held tremendous power and could create nuclear blasts whenever they appeared. To stop that and turn them to humans, he had to date them, something he both liked and despised due to being able to make them happy but also not really get into a relationship. Luckily for him, all of the Spirits understood. In fact, the purple-haired girl who liked kinako bread from before was a Spirit.

Asahi had to wonder how Shido could even breathe.

The plain boy, Mahiro Yasaka, lived with aliens who the Lovecraftian Mythos were based on. Particularly Nyarlathotep ('Nyaruko'), Cthuga ('Kuuko'), and Hastur ('Hasuta'). They all dragged him into messes and pretty much threw himself on them everyday, so he used his skills as a fork wielder (no, seriously) to get them to back off. They also seemed to be obsessed with Earth media and that was one of the reasons they came to the planet to begin with.

Though his methods seemed harsh, the way Mahiro described the aliens in his house made Asahi have to feel bad for him.

The sleazy guy, named Ayumu Aikawa, was a zombie. He had been resurrected by a necromancer and was currently taking care of her, along with a... 'Magical Garment Girl' and a vampire ninja. They caused all sorts of problems to him, but he said he's fine because... he's a zombie. Also he dealt with other undead creatures and Magical Garment Girls quite often. Oh, he was a Magical Garment Girl as well.

After getting through the confusion, Asahi wondered about the vampire ninja thing, the Magical Garment Girl thing, and, even though it seemed Ayumu had sugarcoated things, Asahi didn't think Ayumu was standing up to his rights as a human... er, zombie. (Did zombies have rights?)

The messy haired guy, Yuji Sakai, was also already dead. He was a Torch, a placeholder for a person who had their existence taken away by a Crimson Denizen, a creature that craved existence. He worked with a Flame Haze, people that hunt Crimson Denizens, to stop this from happening. The black haired girl who liked the melon bread was said Flame Haze.

What in the world have I gotten into? Asahi thought.

Well, perhaps it had to do with seeing a vampire stretching out in an empty classroom.

With all that said, they all turned to the guy with the dead fish eyes, who they all had deduced was Hachiman Hikigaya.

Hachiman scoffed as they looked at him and said, "I'm Hachiman Hikigaya. Your standard loner."

Asahi blinked, feeling a bit slighted.

"Hey, is that it?" Ayumu asked nobody in particular.

Hachiman nodded. Akane didn't spring up and say anything, so apparently that was the truth.

With a closer look at his uniform, it didn't seem like anybody else had come from the same school as Hachiman...

Akane then sprung up and said, "Alright, everybody get back to class. I have a universe mix-up to fix."