I recommend a novel to you. It's called "The Eternal Man Who Travels the World". It's a light novel, a derivative doujinshi novel. The story was about an immortal who had lived for thousands of years and traveled to various worlds under the global changes. The first world was a monster hunter, and the second world was a parasite. The protagonist even used a tachi made of ancient dragon material. I hope you like this fairy's recommendation. Muah ~😗