Raidorl Seiken Senki - Chapter 10: A Selfish Betrayal.

What if an alien baby born in the midst of a major conflict on another planet was sent to Earth to save his life? Born with intelligence and the ability to create technology from any material he touches, he was found by a couple in rural Japan and raised like a normal human.Despite his powers beyond reason, living in a peaceful world forced him to restrain himself. He grew up as a young man who loved high-tech superheroes, but never had the chance to realize his dream of becoming a hero.However, everything changed when he and his classmates were suddenly transported to another world—a world of monsters, war, and chaos. Seeing the helplessness of the humans in that world, he realized that this was the chance he had been waiting for.Not with magic, swords, or ordinary physical strength—he would become a hero with technological sophistication that surpassed any civilization!This will be Ren Takamura's story!

Due to investigating an arms case, he was forced to become a gigolo, from then on, the cute little loli, the sweet and pure young married woman, the cold and aloof CEO beauty, and all kinds of other beauties surrounded him.

What would happen, if one day fantasy collides with reality?

- Description from Novelupdates

A man who was once called the world’s strongest agent ended up becoming a teacher after his retirement, to train a new generation of agents. After many years of training his disciples, he was killed at the age of 60 by a secret organization’s ruse and was reincarnated in another world with his memories intact. Though he was surprised by the existence of magic and the strange species in that world, he quickly adapted to his condition as a newborn and took advantage of it. He acquired special magic and gained a massive amount of strength thanks to his rigorous discipline, in order to reach his goal: Resume his career as a teacher which he 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, became a teacher who travels through the world with his students.