Mysterious Transferee (Assassination Classroom Reader-Insert)

As Y/N is walking through the hallway, she saw her teacher looking at his purse sadly. "It's such a nice morning, but why are you sad Koro-sensei?" Y/N asks before she stops in front of him that also made him stop and look at her.

He answers in the same tone as his mood. "I don't have enough money to buy a gelato." Y/N gives a reassuring smile, taking out her phone from one of her bag's small pockets before sending a message to someone, then puts it back again inside her bag.

"Don't worry Sensei. I'll ask someone if they can get one for you and here's what you need for today." Y/N reassures as she hands over the bag.

"Really?! Thank you!" Koro-sensei immediately exclaims in gratitude while he happily receives the items as they continue to walk until they reached the door. Koro-sensei slides the door open and let Y/N go first as Y/N hurriedly goes to her seat.

"Good morning!" Koro-sensei greets the class with new-found joy, but then notices that the class is unusually quiet.

"What's wrong cla--" Before he could finish, he sees the dead octopus pierced with an ice pick, probably because only the handle could be seen.

"Oops, my bad. I mistook it as you and killed it. Bring it here, I'll dispose of it." The red head breaks the silence.

"Alright." Koro-sensei agrees and gets the dead octopus, slowly walking towards Karma.

'Bring it on Koro-sensei. I'll start slowly by killing your soul.' Karma thought as he looks at the approaching teacher while hiding a knife behind his back. Before Koro-sensei reaches his seat, he stopped as the tip of some of his tentacles turns into drill tentacles. He then disappears and reappears in a blink of an eye, holding a missile, tempura bits, flour, sauce and bonito flakes using his other tentacles.

"Karma-kun, let me show you the might of these drill tentacles and the firepower of this missile I filched from the Self-Defense Force." Koro-sensei said as he starts to cook something using the ingredients and cook it using the fire from the missile.

"It seems that you haven't eaten breakfast yet. I whipped these octopus balls at Mach speed. Open wide!" Koro-sensei requests and didn't wait for Karma's response as he puts one in Karma's mouth, but Karma spits it out because of the hotness and covers his mouth with a fist.

"Karma-kun, what I do is tend things, take care of them. Things like assassin's rusty blades. So keep killing me and every time you do, I'll take care of you." Koro-sensei said as he opens his mouth and reveals more takoyaki, continuing to speak even with his mouth agape. "So keep killing me and every time you do, I'll take care of you. By the end of the day, your body and mind will be polished." He moves four tentacles, two on each side, up and down.

The first period, Math, begins. As Koro-sensei talks about their lesson, which is division, Karma takes a gun out of his blazer and aims at him that resulted with the teacher being able to notice it as he calls out. "Karma-kun, it takes longer for the fired BB to hit." Koro-sensei stops and looks at Karma who's still holding the gun. "Since I had plenty of time, I gave you a little nail art." The teacher informs after he had quickly take the gun out from his grip as Karma annoyingly looks at Koro-sensei while his hand has beautiful takoyaki theme nail art.

Koro-sensei then looks at the one who gave the items to him earlier before saying his gratitude. "Thank you Y/N-chan!" Y/N just sweat drops and waves a hand. Now, all of the students' attention is on her. '

What did I do?' Y/N thought as she ignores and just resumes back at taking notes while her seatmate glares at her.

As he sits back down, he thinks about one thing. 'I'll get my revenge on you, L/N-san.'