MTL - People Are In Tokyo, and the Peerless Raptors Are Also Afraid of Hatchets - Chapter 393 Sharp √ Japan Life Insurance

Protagonist travels between different anime worlds to right wrongs and uncover his reason for being along the way.

- Description from Novelupdates

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.

I finally managed to kill the demon lord.

I was proposed to by the Final Boss.