Katainaka no Ossan, Kensei ni Naru

It is an interesting Japanese light novel. It is famous because of its performance, and the viewers are except for it being an anime but it is a light novel in Manga. Its main character is a middle-aged man who turns out to be a sword saint. He is a humble person with his powers because he looks like an ordinary man. But his skills and powers surprised everyone. He has a wonderful strength and shows the viewers funny moments, action fights, and fantasy elements, which makes it popular among its fans.