EDIT (26/5/2018): This chapter has been updated with more context and less spelling and grammar errors.

Hey minna-san! This is BlueSkyBlue here and this idea had been in my head ever since I read the last chapter of the Ansatsu Kyoushitsu manga. I only just got the time to write this as I updated my Crystal Tears fanfic yesterday. I hope you all enjoy this!

Shiota Nagisa is proud to say that he is a successful homeroom teacher to the class 3-5 of Paradise High School. After a month teaching in the class, even taking over the other subjects as the rest of the teachers were too terrified to even enter the class, he had made a lot of progress with his students. Teaching English may be his major, but he had not forgotten how to do his Science and Maths. He was able to handle the work load fine.

Though... He scowled as he reread the message on his phone again.

Shadow. We need your service again. Report to the Ministry tomorrow. Same protocol. -KT

Nagisa sighed in exasperation. His talent for assassination... it is rare skill. Two weeks ago, his old mentor -Karasuma Tadaomi- called him, demanding that he meet up with him.

Turns out that the Ministry of Defense is working on exterminating underground gangs and yakuzas. They were finishing off the baddies just fine, but some are just too dangerous, and Karasuma did not want to put his *coughs*precious wife in danger. Nagisa is the first person that jumped into Karasuma's mind to handle the matter.

It was hard to refuse the request his former teacher asked of him. On the other hand, the offer was quite tempting as the teal head was itching to hold a gun after so many years of not holding one.

The first time he went for a mission, he left his class with one of the substitute teachers the school provides. He had to capture or kill a yakuza leader, and if any yakuza members get in the way, them too. The yakuza group was very known for their underground dirty dealing. Nagisa was honored to say that he pulled off the first case just fine without a scrape of his skin. Things did not go well with his class, however, as he returned to find a horrified substitute teacher who probably go mentally scarred forever.

Of course, Nagisa made sure to punish his class for what they did after that, not before apologizing to the substitute teacher, who is most likely going to end up in a mental hospital like every other teacher who had taught his class before he became the homeroom teacher. Still, he did not want to risk the same incident repeating itself this time. An idea popped into his mind and a smirk crept up on his face.

Now that is a good idea...

A red headed man smirked to himself as his fingers expertly maneuvered the controls on his Nintendo. Several employees around him shot him nasty looks as they worked on their projects and whatnot. They cannot really go up to the man and ask him to get back to work because he has already finished his workload for that day. For someone who just got into their ranks last year, Akabane Karma has easily finished all assignments given to him, no matter how tough they are.

However, there was someone who was not afraid of standing up to the man.

Takanosuke Hikaru, an intern who just started working in the department for a week, slammed his fists on the table as he glared at Karma. "Look, your gaming is causing a lot of noise and is disrupting others who are working! You are not even supposed to be playing games! This is proper working etiquette!"

Karma just smirked. He neatly filed the documents on his desk before packing his Nintendo into his briefcase along with some of his personal belonging. "Well, since I have finished this week's workload, don't expect me to turn up for the next few days. I wouldn't like to be disrupting others when they are working, after all."

With that, he strolled out the office with his briefcase slung lazily over his shoulder. Hmm... There's nothing to do... Maybe he should visit the arcade...

Just then, his phone rang and he took it out an examined the caller's ID. There on the screen was a picture of a tealnette in a dress and a blush on his cheeks. The words "Nagisa" were below the picture.

He slid his finger across the green button to accept the call.

"Yo, Nagisa."

"Karma? Are you free later around six o'clock at night?"

"Yeah, why?"

"I have a favor to ask of you. Can we meet?"

"Yeah, sure."

"Alright, then shall we meet at Isogai's and Mimura's cafe?"

"Okies. What got your panties in a twist, by the way?"

There was a grumble at the other side of the line. "I'll tell you later."

"Okay, okay, I'll see you later, then."

"Welcome to Yuma's Host Club! What would you-" A dark brown haired man greeted enthusiastically but stopped abruptly as he saw his customer. "Nagisa! It's been some time!"

The tealnette smiled bashfully. "Hey Isogai. Is there a place here where I can discuss matters privately? Karma will be dropping by soon too."

"Yo, Nagisa!" A man with chestnut hair popped out. "You can use the VIP room, that should be private enough. You should have informed us earlier if you planned to visit!"

"It was rather unplanned, to be honest," Nagisa agreed. "You guys should join the conversation later, it's something quite important."

Just then, the soft sound of a bell jingle sounded, alerting them of the presence of a new customer. In walked a tall red headed man. He paused at the door and looked around the room, eyes finally landing on the small group.

"Yo, Nagisa, Isogai, Maehara," he greeted with a drawl.

"Come, let's move this to the room." Isogai quickly said as he beckoned them over to a private section of the cafe.

They entered a small secluded area where Isogai excused himself before returning with a tray of pastries and a pot of tea. The four friends sat at a table as they began to talk.

"So what's up?" Karma asked.

Nagisa scratched his head, wondering how to phase his sentence before deciding that he should get straight to the topic. "I'm now a part-time assassin."

Silence.

"Why, Nagisa, I didn't know that you were such a thrill seeker. Aren't you working as a teacher?" Maehara questioned as he helped himself to a Swiss roll.

"It was by request of Karasuma-sensei," Nagisa replied. "He struck a deal with the principal to excuse me whenever I'm taking an assignment to deal with any underground Yakuza and the such. However, the first time I was away... my students got into trouble."

"Trouble?" Isogai arched an eyebrow questioningly.

Nagisa blushed. "You can say they are like a class of Terasakas and Karmas."

Isogai and Maehara winced at the thought of that.

"So what about it?" Karma asked.

The tealnette twiddled his thumbs. "So... I was wondering whether you can take a day off tomorrow to be a substitute teacher for my class? You don't have to do it! It's just that the last time the school issued their own substitute teacher, she got traumatized to the point that she had to be sent to the hospital."

"Sure, why not?"

"Really?" Nagisa looked up hopefully.

"Yeah, I have nothing to do anyways and I have leave for tomorrow already so, sure." Karma agreed easily. He muttered something under his breath which made Nagisa narrow his eyes at him.

"You are not planning anything bad, aren't you?"

The red head just smirked. "No, whatever made you think that?"

It was a normal day in for the students in Class 3-5 of Paradise High. Down at the front row of seats sat a small group who were gossiping with each other. A bald headed boy was throwing paper balls at another student from where he sat, which was by the windowsill. At the back of the class, a blonde girl was writing furiously in a book of hers while a few other girls were discussing about the upcoming anime. A tall, handsome boy lolled back on his seat as he joked with some boys while some girls gathered behind him to swoon over him. Needless to say, they were making their usual racket. However, all of them kept an eye on the door. Rowdy as they may be, they held a lot of respect for the teal headed chibi that was their homeroom teacher.

The door opened.

The effects were immediate. The gossiping group quieter down and returned to their usual seats and the bald headed boy shoved his paper balls into his drawer as he stuck his tongue out to his friend one last time. The girls who were discussing anime sat down and nudged the blonde who was still writing furiously in her book. At the nudge, however, she let out a tiny squeak and quickly shoved the books into her bag. The pretty boy sat up straight before standing up.

"Class stand!"

Everyone jumped to their feet.

Before the boy could greet their teacher, a red headed man with orange-yellow eyes walked in with a briefcase in hand. Everyone froze, who was this stranger? He was dressed smartly, making him look professional. Thoughts ran through the students' heads. Where was their homeroom teacher?

"Good morning class," the man drawled out as he positioned himself in front of the class. "The name's Akabane Karma. I am a friend of Nagisa's, and I will be taking over your classes for today as he is sick. I'm looking forward to working with all of you~"

Some students blinked in confusion while others began to smirk. Oh, they were going to have so much fun with their substitute teacher.

How wrong they were.

The plan was simple, really. Though not all of them are in cohorts, the plan was just to start a fight. That was easy enough, either they make the substitute teacher angry or just throw a punch at the guy's balls or something.

After taking attendance, the class proceeded with the first lesson of the day, which quite a coincidence, is Maths. Time to launch the plan in action.

"I won't be repeating myself," the red headed man began, but was cut off when a punch came flying towards his face. He immediately sidestepped it and grabbed the hand in a vice grip. "My my," he drawled out. "Resorting to violent attacks already? Won't Nagisa be disappointed with you..."

Akari, the boy who struck found his hands tied before he can even blink, wasabi in his mouth which was then tightly taped shut. Tears began to leak from his eyes at the intensity of the wasabi in his mouth.

Karma then positioned himself back in front of the class. His orange-yellow eyes stared at every single student in the class intently. "I understand that Nagisa is a brilliant teacher, I do not know how he teaches you... But as his best friend of nine years, I will say that he is a lenient guy. I am not that guy. As you can see from the example in front of you, I do not tolerate misbehavior."

Goosebumps shot up the student's spines as they stared back at the sadistic man that was their substitute teacher for the day. They should've guessed it... After that first incident, of course their teacher would make arrangements for a qualified teacher to take over for him. But they certainly did not expect this!

Karma clapped his hands. "Alright, back to the topic... I will not be repeating myself so listen to me carefully. I will give you all Math questions and if any of you answer one wrong, its wasabi for you." A creepy smile was on his face as he showed them several large tubes of wasabi.

Dread filled them. They are going to have to focus on this one...

"First question..." Karma put his hands in his pockets as he slouched. "A fruit seller bought 1508 apples, 6246 oranges and 12 dozen grapes. How many fruits did he sell at the end of the day?"

The sounds of pencils scribbling furiously were heard. The students counted, recounted... checked their answers and rechecked their answers.

"7898" They chorused their answers, after making sure that it is correct.

Karma smirked. "Wrong. How did you know that he sold that much fruits at the end of the day? I only said that he bought those fruits, the amount of fruits he sold is unknown."

Half the class mentally groaned while the rest fainted, They were going to have a loooooong day...

How right they were.

"Sensei, are you related to Akashi Seijuro, by chance?"

Karma stared at the blonde girl before him. The girl returned the stare as she repeated her question again. There were no malicious intent in her words. Instead, she seemed to be very oblivious to her surroundings, namely students who were furiously mouthing at her to keep her mouth shut less she unleash the anger of a devil.

He just smirked and patted the girl on her head. "You, my dear, are going to be my best buddy today," he announced.

The boys paled.

Nagisa whistled to himself as he playfully played with a knife in his hand. He had managed to pull his mission off successfully. As he slowly made his way to his class, he pocketed the knife. There was no way he was going to have a knife in the presence of his students. He opened the door.

Silence.

The tealnette stared at his class in horror. There were students who had fainted with their mouths taped shut. He can guess what was inside their mouths even if he was given one chance. Some others were cowering at a corner of the classroom. He did a quick headcount and knew instantly that a few of his students had ran away from the devil that was Karma.

He spun to glare at the smug red head who was standing at the middle of the classroom.

"Karma," he growled. "I told you to give them a firm hand, not this!"

Karma crossed his arms defiantly. "I did not nothing wrong. It's not my fault that they can't take wasabi, they should be ashamed to call themselves Japanese."

Nagisa gave him a half-exasperated smile. "Thanks, by the way... Remind me not to ask you to teach the class when I'm on another mission next time."

"Will do."

And that's it! It isn't much, I know, I tried to make it as humorous as possible but um... yea. Do tell me whether you guys want more chapters where the Class 3-5 react to people like Kayano, Okuda... maybe even Terasaka teaching them. I was also thinking about writing where the class reacts to Karma x Nagisa for the fujoshis here, and also a Kayano x Nagisa one for those who ship this pairing. Tell me what you guys think! I do hope that you all enjoyed this!