Akuyaku Reijou ni Nanka Narimasen. Watashi wa『Futsuu』no Koushaku Reijou desu! - Chapter 149.1: Stirring up a provocation.

He became a teacher at the best magic academy in the empire.
….For being mistaken for someone else.

The protagonist, a famous YouTuber known for playing the game trilogy “Tril Trilo Trilogy,” finds himself possessing the final boss of the game world.Before the release of the new instalment in the series, he receives an offer from the game’s developer to play a prequel, “Part 0,” which explores events that occurred before the first instalment. Since he is a fan of “Tril Trilo Trilogy,” he eagerly accepts the offer.However, through some twist of fate, he wake ups in the world of “Tril Trilo” in the dreadful body of the final boss of the trilogy, a character named Frank Wonderstein.

Ding![The Host has died!]A system message popped up in front of Nell's body after his last dying breath.Ding![Dark Evolution has been activated to absorb the death essence of the host.]And then he opened his eyes to find himself in the past right before the battle started.'Ah! Am I back to the past?'Ding![Please choose a partner to start the Dark Evolution process.][Partner Condition: Must be a living creature from the Monster category, not the Human category][Partner Gender has to be Female.]'Partner? A monster?'Nell's heart pounded in his chest, and he felt a cold sweat coming on.'A female monster?'

The hearse with the weird odor slowed to a stop before the entrance. The sound of pebbles could be heard bouncing on the ceiling. There were footsteps coming from the corridor, and there seemed to be someone sawing next door. The door knob to the room rattled slightly, and the faucet in the bathroom kept dripping even though it had been screwed shut. There was a rubber ball that rolled on its own underneath the bed. Wet footsteps started to surface one after another on the floor.
At 3 am, Chen Ge held a cleaver in his hand as he hid beside the room heater. The call he was trying to make was finally answered. “Landlord, is this what you meant by ‘the house can be a little crowded at night’‽”

- Description from Novelupdates