World Teacher

He was once called the world’s strongest special agent. But after his retirement, he became a teacher in order to forge a new generation of special agents.
After many years of training his disciples, he was killed at the age of 60 by the ploy of a secret organization and was reincarnated in another world with all his past memories.
Though he was surprised by the elements of magic and the strange species of that world, he adapted very fast to his condition as a newborn and took advantage of it.
He acquired special magic and gained a massive amount of strength following his tight discipline, with a single goal in mind: Resume his career as a teacher which he had left halfway through in his previous life.
This is the story of a man, who, based on the memories and the experiences of his previous life, becomes a teacher who travels through the world with his students.

Raw: https://ncode.syosetu.com/n4237cd/