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(Last march)

Karma sauntered into the office with a look far too relaxed for his current circumstances; He had gotten in trouble for fighting for the twelfth time that year. Well, they called it 'fighting' but despite all his talk his opponent was such a weakling it was more akin to 'beating up'.

"Sup, Sensei." The red head said as he walked in, nodding at his teacher, Mr Kensaku Ono. His devilish grin widened then he nodded at the bandaged older student sat next to him in acknowledgment. "'sup Hakaze."

Hazake glowered at him with a mixture of contempt and fear. His arm was still in a sling after his fight with Karma.

"Akabane, I suggest you adopt an attitude more fitting for the seriousness of this situation." Ono-Sensei growled. He was pissed off, Karma could tell- The guy might even give him a detention.

But Karma wasn't too worried; He liked Ono-Sensei. The guy got him. His parents had been dropping him off at boarding schools since he was eleven. The teachers were always such a pain, trying to force him to follow rule after meaningless rule, then griping when Karma wanted to do his own thing.
He was labeled as 'challenging' and treated like a burden by most teachers who saw him as nothing but trouble. But Mr Ono was different; So long as Karma got the grades, the guy let him skip class, and miss homework.

"Karma, sure your behaviour is difficult, but you scored 2nd in the whole school, I can't complain."

He promised to always support the troubled child as long as Karma was in the right.

Karma trusted him. More than any other useless adult, more than any other human, including his parents.

"Okay, so I admit that I might of gone too far, but Hakaze-Senpai was bullying Ritsu-Senpai. I think I was right to intervene." The red head said. Ono-Sensei glared at him from over the desk.

"Hazake is the top student in his year! If his injuries effect his test results that could effect my appraisal!" The teacher yelled, slamming his fist into the wooden desk, knocking over a pencil pot. "You think I give a damn if he was picking on some E class nobody like Ritsu Yoshiro!"

Karma stared at his teacher, mercury eyes widened slightly in disbelief. "You said you'd be on my side, sensei- "

"I thought you had potential, Akabane, but you're a good for nothing trouble maker! This incident could effect my pay!" Ono-Sensei yelled, standing up out of his chair. He spat droplets of saliva into the air as he shouted. "Even your good grades can't save you now. I've secured your transfer to E class next year."
E class?! Were all the rejects of the school go?

Grades.

Appraisals.

Pay.

Karma's expression darkened. He realised he was a fool for thinking this teacher cared about him as a person, that Ono-Sensei 'got' him. This man only cared about Karma's grades.
Sensei wouldn't stand by him at all, he'd drop Karma as soon as he became an inconvenience; Just like his parents. Just like all adults.
Something inside Karma snapped, and a wild rage was unleashed.

"You think I give a damn, you piece of shit!" Karma roared, slamming his fist into the desk so hard the wood splintered all the way through. Ono-Sensei and Hakaze both jumped away.

"You aren't a teacher to me anymore! You're dead to me!"
He stormed out, not before throwing his chair across the room for good measure. He heard it shatter a window but he didn't give a damn.
He kicked the door out the way almost hitting it off it's hinges, and shoved his hands in his pockets, not caring that his fist was bleeding.
"I will fucking burn this school to the ground."

A few weeks later, Kensaku Ono was brutally murdered.

Nagisa was back in the depressing cesspit known as the 'E class lounge', a small room with an assortment of ratty, half broken chairs and one large table covered in various stains.

He was sat playing cards with Isogai, Kayano, and Isogai's blond friend Maehara. He could easily see Kayano's cards, and Maehara's moves were predictable, but still, Nagisa was purposefully loosing (because nobody suspects the weak). He was trying to get as much information out of them as they could, (although Kayano was too new to the school to know much).

"Hmm, so you ran into Karma Akabane?" Maehara said, as he picked up a card. "Everyone says he's scary, but he's alright s'long as you don't piss him off."

"What kind of things piss him off?" Nagisa asked, making himself sound a little nervous. Maehara laughed.

"Don't worry! It's not his style to beat up shrimps like you- no offence." The blonde said, with a slight smile. "He usually goes after bullies, so most of the 'big five' are terrified of him. He even had serious beef with a teacher once."

Nagisa faked a look of surprise. "A teacher?" He gasped. Meahara dropped his voice.

"Yeah- Ono-Sensei, the guy who died." The blond said in a half-whisper. Isogai gave him a disapproving look. "I know you're not suppose to talk bad about the dead or whatever, but he was a real nasty piece of work. He betrayed Karma and threw him into E class in the first place."
Nagisa was about to ask more, but suddenly, a hyper-active ball of energy burst into the room.

"Hey there boys and girls!" A voice enthused, everyone looked up to see a black haired man standing in the doorway. "I'm your new teacher, you can call me Koro-Sensei! It's fantastic to meet all of you."

There was a chorus of obligatory 'nice to meet you's ' and an undercurrent of mutters;

'So he's one of those teachers who pretends to care, lets see how long that lasts.'

'Why's he so upbeat- doesn't he know he's been lumped with the worst class'

'What the hell is he wearing?'

The class' collective self-esteem was so low it was almost tangible, like a big black hole sucking life out of the room. Nagisa looked at his Master curiously- That was a strange persona he had decided on, surely he'd have more time to work on the mission if he was playing the part of 'lazy teacher' instead. He'd also stick out less.

"Okay everyone! I want you all to tell me your names!" Koro-Sensei said with a bright smile "So we can have a proper introduction."

"You know, class doesn't start till Monday, you don't have to be here." A girl with long blonde hair said disdainfully.

"But I really wanted to meet you guys now." Koro-Sensei said, a slight whine to his voice. The God of death was wearing black western style teacher's robes and mortar board with a over-sized tie, it made him look strangely out of place in the dank E class setting.
He had one of those faces that was vaguely good-looking, but still easily forgettable. He could easily use different expressions to become a completely different person.
Right now with his goofy smile and bright eyes he seemed wild, eccentric and enthusiastic.

"Whatever." The blond haired girl said. "The name's Rio Nakamura. Nice dress by the way."

"These are robes!" Koro-Sensei declared, he pulled out a register from his sleeve. "Okay! Lets see who from class is here! When I call out your name I want you to tell me one thing about you."

So my master is going to act as my school teacher; This'll be interesting. Nagisa thought to himself. Shinigami-san had been a university lecturer before on a mission, but teaching a bunch of rag-tag kids would be very different from that.
Koro-Sensei read out the register, the kids answered with varying degrees of enthusiasm.

"Hinao Kurahashi- "

"Here! And uh- I like animals!" A girl with short curly hair smiled.

"Ryoma Terasaka."

"Here. And I think this is a stupid idea."

"Nagisa Shiota!"

Black eyes made contact with blue for a fraction of a moment, but neither male made any indication that they knew each other.

"Here- and I'm new. I hope I get along with everyone." Nagisa said, with a sweet smile. Suddenly, the blond haired girl, Rio Nakamura, grabbed him and pulled him into a hug.

"Aw! You're adorable, of course you'll make friends." She snickered. Nagisa caught Koro-Sensei smirking at him for a fraction of a second over Rio's shoulder.

"Yes! Since your all going to be living and working together over the course of the year, this class will be like family. We'll make sure to support each other ." The teacher said with a dreamy expression in his normally unreadable black eyes.

"Heh- stupid idealist, wait till reality bitch-slaps you in the face." Terasaka grumbled.

"Lets give him a chance." Isogai whispered to him, being his usual nice self. "Anyway, it's almost dinner time- who's on shift to cook today?"

So the E-class had to cook for themselves while the main school got provided for in a fancy cafeteria. Nagisa had to wonder why the Chairman ever thought this school system was a good idea. Maybe he was just a psychopath who wanted to research the effects if inequality?

"Fear not class! I have taken it upon myself to cook dinner for you!" Koro-Sensei declared, that stupid grin on his face. The class looked downright shocked.

"Wow! Really!" Kurahashi said, beaming.

"That bastard better not of messed up our food supplies, if he's burned them imma kill him." Terasaka growled. The teacher paid no heed to the insult, instead he just turned to the class.

"Gather up people from the dorms and follow me!" He said, leading them to the E-class cafeteria (which was just the classroom with the desks and chairs put together). Nagisa had seen his master put on countless personas, but non like this before, his personality just seemed so- .. Bright.

Once they walked inside, the entire class' face lit up (even Terasaka looked begrudgingly impressed). Nagisa pretended to be surprised also, but of course, by know he knew that anything his master did would be amazing;

A spread of delicious looking food was laid out on the old wooden desks. For a moment, the crispy roast potatoes and aromatic soup almost made the dingy 3-E classroom seem like a fancy restaurant. There was hot-pot, tasty looking fish dishes and more arranged in a buffet.

"Okay class! Dig in!" Koro-Sensei declared. The class practically ran for the food, there was a few 'thank you's' shouted over the crowd. Nagisa followed.

"Wow, Sensei, did you hire people to make this?" Isogai asked, his voice filled with wonder (its only food! Nagisa thought). The black haired man shook his head.

"No, I made it myself!"

"Whoa! No way!" The class looked impressed. "Are you a chef?"

"No, no, it's just a hobby." Koro-Sensei said, he checked the register. "Let's see- we're still missing Akabane Karma."

At the mention of Karma's name, an uncomfortable, stifling silence filled the class like the teacher had uttered something taboo.

"Don't expect to see him around much, sir." Isogai said, glancing to the side. He looked as if the words left a bitter taste in his mouth. There was another moment of awkward silence. Nagisa caught his master's eye, and the man nodded.

"Hm, We'll see about that." Koro-sensei said quietly, then his smile widened again. "What're you waiting for? Dig in boys and girls!"
Gradually, the noise level went back up again as people started chatting normally, as if Karma hadn't been mentioned. Nagisa took a plate, and filled it up with food, going to sit with the others as if he was an ordinary student.

Later that evening, when the other boys were in the dorm room chatting away, (Besides Karma Akabane who was wandering off God knows where.) Nagisa walked through the wooden corridors silently on bare feet, looking through the dirty window at the main building; It looked like a castle from this distance. (Was the killer hiding out there?). It dawned on him how impossible this mission really was. For all he knew, the killer could be in a different country by now.

Suddenly, Nagisa felt a strong arm wrapped around his neck. His instincts kicked in and he automatically went to pull away from his assailant, only to have his wrists grabbed and pulled behind his back also. He could feel his attacker close behind him.
"Got you~." A playful voice whispered into his ear. Nagisa rolled his eyes- He should of known.

"Well done, Master." He said sarcastically, trying in vain to pull his arm free (but the difference in strength was too great). He could feel the black-haired assassin smirking behind him before letting him go.

"You have far too many openings,young Nagisa." The God of death chided. He had changed out of his ridicules teachers robes and was wearing a non-descript dark outfit that blended with the shadows. Nagisa didn't even stumble, instead he just turned around to face his master.

"What about you? You're the one trying to play detective instead of just killing." The blue haired boy said quietly, a skeptical edge to his voice. "And what's with your persona- It'll be more time consuming pretending to be a teacher who cares. It'd be more effective if you were just consistently lazy."

"Short-sighted as ever, Nagisa." Shinigami said, with a shake of his head. "If I want information of these little outcasts, I need to be someone they can trust. Sure, after being let down by adults so often they might be suspicious at first, poor things, but they're so starved for attention and approval, it'll be easy to get them under my thumb."

"How typical of you." Nagisa said- If he wasn't so used to it, Nagisa would find it jarring hearing Koro-Sensei talk about the E class so flippantly after acting so kind to them hours earlier. "But what if the killer isn't in E class."

"I'm certain they are." The God of death said- He was also so damn sure of his own opinion, it was fact to him (to be fair, he'd never been wrong that Nagisa knew of). "But there's one pupil I might have a problem connecting with- That Karma Akabane. I read his file, he doesn't take well to authority."

"That's a pity. He's already my number one suspect." Nagisa said, thinking about their meeting earlier today. The way the red haired boy had looked at him with wild mercury eyes.

"That's why you have to get close to him. Find out the truth so we know if we should kill him!" Koro-Sensei said, then smiled. "It'll be so nice for you to have a friend your own age!"

Something about his tone made Nagisa feel sick. Oh well. He'd just get a confession out of Karma, kill him, then leave this hell hole simple as that. He bowed.

"Yes master." He said solemnly. The black haired man grinned.

"Good, now hurry to bed young Nagisa! I'll be thinking of you sharing a room with a dozen other smelly boys in this shack while I'm sleeping peacefully in my luxury teacher's room in the main building~"
The blue haired boy frowned and turned to snap at him, but his master had already disappeared into the shadows.

(A/N: So In this story, Koro-Sensei has both his teaching persona, and his ruthless assassin identity, Will he become the mask or stay true to his original motives till the end? Even though he's acting like the Koro-Sensei from the show, there's still a lot of differences; For example, in this story he gave the kids food to win them over (Kind of like Takaoka did) but in the show Koro-Sensei never uses cheap tricks like that and instead lets his actions as a teacher win the kids over.

Nagisa and Karma will soon begin their ill-fated friendship...

So who do people think the killer is so far? leave reviews!