Yamasachihiko is a Transient hunter and conqueror of the mountains in the other world of Takamagahara. In Tokyo, he joins an academy where he can learn about nature conservation, specializing in mountain protection. He long considered his brother—a fisherman of the sea—both his idol and rival, and tried to exchange tools with him to see what it was like to be in each other's shoes. It was at this time that Yamasachihiko lost his brother's treasured fish hook. Which he has been looking forever. 