World Keeper - Chapter 1041: Into The Pit

An unnamed 34-year-old Japanese NEET is evicted from his home following his parents' death.

Upon some self-introspection, he concludes that his life was ultimately pointless.

Walking down a street he intercepts a speeding truck heading towards a group of teenagers, in an attempt to do something meaningful for once in his life he manages to pull one of them out of harm's way before getting himself in the way of the truck and dying.

Awakening in a baby's body, he realizes he has been reincarnated in a world of sword and sorcery.

He resolves to become successful in his new life, discarding his past identity for his new life as Rudeus Greyrat.

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

‘Less than a month old… I became the the great empire’s treasured princess…!’

“Teacher, you know me. I’m usually a good student, with nearly 100% attendance, and I’m also eager to help the people.

Yesterday I flew to the coast to fight monsters, so…”

“Teacher, you know me. Which teacher is not full of praise for me, but things are prioritized. Yesterday happened to be the Ghost Festival. Hundreds of ghosts walk at night, so I…”

“Teacher, you know me well. I am an activist in our dormitory. Every day I call them to go to class, but under special circumstances, so…”

“Teacher, I’m a foreigner, I don’t understand what Xie said, and I didn’t know there was a class yesterday, so…”

The teacher took off his glasses and rubbed his temples, “I can tell that everyone in your dormitory has stunts, but this is by no means a reason to skip class! This class! This year! You guys are all done!”

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Another version of the introduction: Ultraman Delta was living in another world for unknown reasons. Originally, he wanted to be an ordinary college student, waiting for one day to find a way to return home.

But the sudden appearance of a monster disrupted his plans, and he also discovered that his roommates were not ordinary people either.

- Description from novelbuddy