The Devil Duo (Karma x Reader)

Part 30 (Final boss time)

Cake pieces splattered everywhere, as an all too familiar voice rang through the now completely silent area.

"Happy birthday."

"Shir-no..." Nagisa said surprised, as Korosensei looked at the man.

"Yanagisawa..."

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"The time is ripe." The mad scientist said while stepping out from the shadows. 

"Let me give you the gift of the world's cruelest death." He said in a voice completely void of any emotion, except the promise of malice, and some underlying satisfaction.

Behind him as what looked like a human, that was covered in a ziplock bag. The figure slowly dragged the zipper down, as two glowing eyes meet Korosensei's.

"Sensei... you know who I am, don't you?" A voice that sounded so altered, you wouldn't believe that it came from one single human.

"Why don't I re-introduce him to your students, too?" Yanagisawa asked even though, it was more like a demand, as he left no room for any objection.

"He's the man who stole the name 'the Reaper' from that octopus. And..." He said as the figure suddenly expanded into what looked like a tentacle monster. The antimatter tentacles replaced very body part of his entire being, leaving no recognizable human-like features on him.

"... as of today. He's the new Korosensei." Yanagisawa said as he walked in front of his creation.

"He's gotten the same modifications as the octopus. The only difference is that... he begged for them." He said as he stared down Itona and Kayano. 

"Unlike the botched Itona or my little sister over there." He said, continuing his speech that was coming close to being a mocking taunt. 

"Can you imagine? A man who overpowered you singlehandedly even as a human, now has both incomparable tentacles and hatred." He said as the creature launched forward towards Korosensei.

"Die!"

At the sheer impact of the blow, all of class E was sent flying several feet away.

"Sonic boom..." The scientist said calmly while watching Korosensei struggle against his former pupil. "His tentacles have an initial velocity of Mach 2, and they can reach a top speed of... Mach 40.

"H-his basic performance is doubled... Korosensei..." Y/n said as she looked at how she and the rest of the student's main teacher got beaten up by tentacles at such a speed that their eyes almost couldn't keep up.

"You... You monster! Why do you always have to do this?!" Y/n shouted as angrily tears fell down from her face. 

"Why do you have to ruin so many lives!?" She said as Karma had to restrain her from attacking the mad scientist.

"Y/n! Calm down." Karma said, trying to get through to his girlfriend, who he surprisingly had a very hard time to restrict.

"You're always watching from a safe distance while others take the suffering from your experiments!" Kayano shouted out angrily as both girls gave the man a truly angry and venomous glare.

"Oh? I'm not prepared to die? Is that what you think?" He asked as he took down his white hood, as he pulled out a syringe with some purple liquid in it.

"Hey, t-that's..." Sōsuke said not believing what he was seeing as the mad scientist injected it to his neck.

"It... It can't be..." Okuda said completely horrified.