Martial King's Retired Life - Chapter 33Book 15:

It has been more than ten years since he was transported to another world. The protagonist Deris Fahrenheit, who has became a magician with special circumstances, was freely enjoying his life in this world. However, a girl appeared before him and asked him to make her his disciple. That girl seems to be a transported person――

It’s a story of him who becomes the girl’s teacher and trains her to achieve her revenge (?) in otherworld.

Lin Jin never imagined he would ever transmigrate. And to such a peculiar world at that. Here, deadly beasts were regarded as sacred, and thankfully, he owned a museum for deadly beasts.

“Those who defy the heavens must be prepared to pay the price.”Zhu Rong dared to forge a divine grade weapon in the mortal world, an act the heavens deemed a challenge to their authority.In response, the tribulation descended with fury, striking him down and ending his life in a blaze of divine wrath.But death was not the end.In the moment his soul scattered, he awoke once more... in the body of his 17 year old self.With his memories intact and the mistakes of his past laid bare, Zhu Rong is granted a second chance, to repair the regrets that once shackled his heart, to reclaim the strength he once lost, and to finish the masterpiece that cost him everything.This time, he will forge his legend anew.And this time, not even the heavens will dare to stand in his way.

This is a story of a man named Kim Sae-Jin, who one day, inexplicably wakes up as a Monster. Follow him and his perilous journey to get his life back as a Human, all the while growing even more versatile as a Monster in the process. This should be… complicated, somewhat.