Due to a series of consistent and irrefutable failures on your part, you are a new student in class 3-E belonging to the junior high school Kunugigaoka.

Upon entering the classroom, your eyes land on a... Being, of whomst is roughly three meters tall with a body made tentacles similar to an octopus. But... He's yellow. The debrief you were given was brisk at best, consisting of whatever could be said on the walk to the room.

"Koro-Sensei" is what they call him. Reportedly he can change the color of his skin according to his feelings, and basically cannot be destroyed by any normal means. He's invincible, and extremely hard to even lay a finger on. But he's shockingly amicable, even enthusiastically kind. He's got an unbeatable confidence rarely seen in today's modern world.

But then again, he is an alien planning to destroy the Earth.

"So you're a new student in class 3-E I was told so much about! Please, do introduce yourself!"

Koro-Sensei speaks in a playful and theatrical voice. It's disarming. If you didn't know his power, you'd think he wouldn't hurt a fly.