Slithery Paradox

Characters: First Shinigami; Yukimura Aguri; Koro-sensei

March 12, 20xx, 9:15 PM.

It was a normal evening for everyone, but for the First Shinigami and Aguri, it was a momentous moment for them.

Neither they had expected, even people around the world, that this day...will be going to be the weirdest day ever.

For the first time, he and Yukimura Aguri had finally touched, after a year of comfort and soltitude, with a glass barrier separates them.

Aguri looked at the assassin's eyes as she smiled, feeling the warm touch of the glowing tendrils that came from the assassin's black locks. The Shinigami looked at Aguri with a gentle look on his face as he behold the sight of his beloved.

"I know you can do it, Yukimura-san," he spoke gently, as he touched the glass barrier that separates them and placed his forehead on the glass. Aguri followed, her hand mirroring his own, her own forehead touched the glass as she chuckled.

"I know. Say, you can call me Aguri from now on, for you know, we are now close to each other," she spoke as she looked at Shinigami's eyes once again.

The Shinigami widened his dark eyes as he stared at Aguri's own, a bright smile formed in his lips, "Really?"

Aguri laughed as her voice chirped up, "Sure, why n-"

She was interrupted when a blast of light flashed brightly and a blast of cold wind blew behind Aguri's back, making the two jump up in surprise, the Shinigami's little tendrils started to retract back in his dark hair. He squinted at the bright light, while Aguri had yelped. Papers were strawn everywhere, as the cold wind blew them away.

When the bright light faded, the assassin glared at where the light originated and saw a strange portal.

Suddenly, something big and yellow pops out of the portal, and crashed on the floor, landing besides Aguri, who screamed and jumps towards the opposite direction.

"NYUYA! THAT HURTS!"

The two stared at the speaker in shock. Out came an octopus-like creature, wearing a black and red academic robe with a huge necktie, an orange crescent moon etched on it. He was yellow, his round head bears pinprick eyes and the widest smile the two had ever seen. A graduation cap with an orange tassel was perched in his head. His tentacles were slithering, while he was clutching his head in pain.

The Shinigami and Aguri gaped like fishes out of the water as they try to ponder on the sight in front of them.

"Ugghhhh...That is worse than trapping me in my Ultimate Defense form..." the octopus groaned, as he winced on the pain. He stood up, as his pinprick eyes started to clear out the fog in his sight. He had looked around, still nursing his throbbing round head, and saw the two, who was still gaping.

Suddenly, his pinprick eyes widened as he approached the frightened woman. "Aguri?! How are you here? It is impossible!" He reached and touched Aguri in the shoulders, shaking her gently.

"Stay away from her, you creature, or I will kill you..." the man glared at the octopus, pounding on the glass angrily.

The octopus heard the Shinigami's warning and stopped shaking Aguri, releasing her. Aguri was still frozen in place.

"Sorry," the octopus apologizes as he turned to look at the man, who was still glaring, "And as if you can escape there."

The creature's head changes color, green and yellow stripes appeared, making the Shinigami being infuriated further.

Aguri snapped of her reverie and politely asked the creature, "Um...hi? Who and what are you? How do you know my name?"

The octopus looked at Aguri happily and raised his main tentacle, signalling for Aguri to hold it and shake hands, " By the way, my name is Koro-sensei, yes, I am an octopus and a teacher, and I could say that I am from the future!"

"A teacher?" The Shinigami and Aguri asked the octopus, while the said octopus nodded too fast.

"Glad to meet another teacher,"Aguri smiled nervously as she shook hands with the octopus, which was now dubbed Koro-sensei. She stared at him, and feels something weird.

"He is something familiar. Where do I see him?" she thought to herself.

The Shinigami was not impressed, "From the future? Tch, as if I could believe that. Time travel is impossible!" he argued.

The octopus laughed as he touched the glass which separates him from the infuriated assassin, "Nurufufufufu~ I could tell you this, in a few months, you will eat those words you have spoken today."

The assassin's hands shook and started to wriggle like tentacles, while his eyes glowed red as he looked at the sniggering octopus in anger, "Why you-"

"Shinigami-san, calm down!" Aguri scolded the assassin, making the assassin stop and folded his arms in annoyance, still glaring at the octopus. She looked at Koro-sensei, who was starting to fidget on his crescent moon tie.

"Well, Koro...sensei...what brings you here? It is not everyday you can meet a...time traveler here, more like an alien," Aguri asked, earning a wince from the octopus.

"What are you, the Doctor from Doctor Who?" The Shinigami commented as he smirked, earning a narrowed glare from Koro-sensei.

"I am not an alien! I was born and raised on Earth, you know! And I have you know, the Doctor is only fictional, not me!" Koro-sensei childishly screamed, as steam started to come out from his 'ears'.

The Shinigami hollered and whistled mockingly, as Aguri groaned. Ever since the Shinigami was experimented by his fiancè, he seems to have a difficulty in hiding his emotions and desires. And that means being a pervert, a petty and proud person rubbed off him.

"Shush," Aguri scolded the hollering assassin, as she started to notice the papers and stuff strawn around the place. Out the corner of her eye, she noticed a roll book not far from where Koro-sensei landed.

While Koro-sensei and the First Shinigami were still glaring at each other, Aguri picked the roll book and read the front cover.

Kunugigaoka Junior High School

Class 3-E

Roll Book

Aguri was confused. She had remembered she left her roll book at the Class E building, as she was the homeroom teacher of the Class E of Kunugigaoka Junior High. She noticed the small details of the book, and see that it was kinda old and worn out. Scratches and small stains lined at some parts of the book cover. Aguri noted that her own roll book was kinda new, for it was still the start of the school year.

"How come Koro-sensei possessed this?"

She opened the roll book and read the contents inside, her eyes widened as she scanned the front page.

It was the names of her current students, but with a few unfamiliar names added on it. There were also little octopus doodles around the page.

Aguri would find it cute, but her mind couldn't comprehend the fact that Koro-sensei, whom she had swore she had never met him in her life, has her roll book.

She looked at the two men (?) behind her, and she could swear she wanted to slap their heads at their childish glares shooting at each other. She turned a page again, and this time something fell out.

She picked it up and realized it is a photograph.

Her dark eyes scanned the photograph and gasped quietly.

The photograph has her own current students on it, with few additional faces on it. Koro-sensei was there, there are two adults standing in the background, a purple-haired girl in a student's phone, a silver haired boy with a bandana, and it even had a student who have exactly resembles her younger sister Akari, only with green hair.

What's weird is she is not in the picture.

She needed answers.

She turned around and decided to confront the octopus, who was still glaring at the dark-haired test subject-slash-assassin on the other side of the glass wall.

"What is the meaning of this?!" She spoke harshly, holding the roll book and the photograph tightly, her usually kind eyes narrowed.

Koro-sensei and Shinigami's arguement stopped at Aguri's outburst, the two of them confused on what Aguri was talking about, until Koro-sensei noticed what Aguri was holding. He gasped as sweat started to form in his head.

"Why do you have the roll book? This is my roll book, this is my class! Why do you have this picture? These are my students, why are you here in this picture, along with these people I don't know? Why am I not here?" Aguri yelled, raising the photograph for emphasis.

"Who really are you?!"

Koro-sensei's head bowed down as the Shinigami looked at the photograph in awe.

Aguri's voice was raised in anger as she held the roll book tightly, "Can you explain to me why are you-"

"Because..." Koro-sensei spoke quietly, his pinprick eyes stared at Aguri's dark ones, while the dark-haired assassin looked at the two with confusion.

"Because what?"

Koro-sensei took a deep breath as he let the truth out, "As I said, I am from the future. In my time, they become my students. And I become their homeroom teacher."

The Shinigami and Aguri gasped in surprise at the revelation.

"But I am their homeroom teacher!" Aguri spoke in a raised voice, shaking her head in disbelief.

Koro-sensei stared at Aguri with sadness in his pinprick eyes, while Shinigami narrowed his eyes at the octopus.

"Not anymore."

"What do you mean..Not anymore, octopus?" the Shinigami angrily questioned the octopus, while Aguri had tears in her eyes.

Koro-sensei looked at the Shinigami then at Aguri. His permanent smile was there, yes, but his eyes showed emotions of grief and sadness. He sighed deeply, as his eyes spotted a huge gift box with a black fabric inside it.

His tentacle reached the gift box and grabbed the black fabric with care, earning a surprised look from Aguri and a glare from the Shinigami.

"Hey, Aguri gave it to me! Take it back!" the angry raven-haired man yelled, as Koro-sensei stared at the black fabric.

It is a huge black necktie.

Koro-sensei laughed gently as he held the necktie carefully, lost in the memories, "I remember she gave me something like this at the day we first touched. It was a necktie too, you know. I remember her smile when she gave me this, and I remember how at first I kinda disgusted at her fashion choices. But when her precious light faded away from me, I started to realize its importance. Her memory...this was the one who keeps me grounded. The one who made me remember her after all these months...and the reminder of my promise to her," he spoke sadly, as his tentacles traced the fabric before putting it back in the box, "I always carried her gift always, to remind me of the promise to teach her children. That is why I became a teacher."

Aguri stared at the sad octopus, pondering on his words, as she saw the octopus touching his own necktie with a crescent moon emblem on it with a longing look. Her mind was confused at first at what the octopus was babbling about, until she had focused on what he had said.

I remember she gave me something like this at the day we first touched. It was a necktie too, you know. I remember her smile when she gave me this, and I remember how at first I kinda disgusted at her fashion choices.

She stared at the crescent moon necktie of the octopus, then at the necktie on the box. She had noticed that besides the crescent moon emblem, the neckties looks exactly the same.

Now to think about it, Koro-sensei's voice was similar to someone she actually knew, just a little happy and high...and she just noticed it.

Her eyes widened as she started to put two and two together, and it seems the assassin did it too.

"What...the...heck," the Shinigami slowly spoke, as his eyes widened at the realization, "It can't be!"

Koro-sensei stopped at what he did and cocked his round head in confusion, "Can't be what?" he questioned in a high-pitched voice, but suddenly his grin grew wide as he also realized what the two was thinking about.

"YOU CAN'T BE ME!" The assassin screamed in horror, as he pointed at the octopus in accusation.

"Yes, you are me," Koro-sensei sniggered, his head changes color as green and yellow stripes appeared, "Nice to meet you, human me!"

"I BECAME YOU?!" The Shinigami screamed again, his eyes still widened in shock, his face scrunched in disgust.

"I am very much afraid, Shinigami-san," Koro-sensei replied.

The Shinigami looked at the octopus up and down as he still screamed in horror, "I BECAME A HUGE UGLY AND CHILDISH OCTOPUS?!"

Koro-sensei was offended at his past self's words, his head turned red in anger, yelling childishly, "I AM NOT CHILDISH! AND I AM HANDSOME LOOKING!"

Omake:

"I am glad that you became a teacher," Aguri commented, a joyful smile graced her angelic features.

"Oh, I can't believe that I became one too. Your students are sweet and brilliant, and your sister is exceptional," The octopus sat at Aguri's table, as he decided to grade at Aguri's students' testpapers.

Aguri grinned as she was delighted to hear those, "Glad to hear about that, even though I kinda found out that my fate will be sealed this midnight."

"Kinda weird Yanagisawa hasn't come in yet and see the scuffle here," Koro-sensei commented as he played some games on his smartphone.

"Yeah, it was kinda weird," the Shingami's voice was low as he still glared at the octopus, arms folding in a childish manner.

"Nah, few hours from now, something will happen that will sent him running. Well, this will cause a paradox, now that you know about the information," Koro-sensei shrugged.

"I am sure we will still carry on, even though we know what will happen," Aguri spoke, a smile still gracing her features.

"Well, why did you change?!" The Shinigami still glared at the octopus, his face still scrunched in disgust as he found out he will become a real-life alien-looking creature who can speed up to Mach 20.

"To be honest, I still miss this human body of mine. In that body, I am handsome and can be called a pretty boy with great fashion choices, before I go on rampage and destroying this damn place...But I love this form now, I am now a teacher, by the way...but if I still had this handsome face, girls would prefer me than Karasuma-sensei!" Koro-sensei spoke happily.

The two was confused at what the octopus was babbling about.

"Eh? What the heck are talking about? Who's Karasuma?!"

A/N: This is a kinda long chapter I made, and it tackles about time travel!

This is kinda based on a 'what if' scenario of what if Koro-sensei was given a chance to go back to the past, and meets Aguri again. This is originally a short incorrect quote I made too, just made it longer.

And because it is a time travel fic, Doctor Who was referenced here! And sorry I just ended it there, it became too long to continue.

Don't forget to read 'Hidden Within a Mysterious Fob Watch', which is a Doctor Who/Assassination Classroom crossover!