Isekai Tennis Musou: Tennis Player toka Iu Nazo no Otoko ga Chotto Tsuyosugiru n desu kedo!
異世界テニス無双 テニスプレイヤーとかいう謎の男がちょっと強すぎるんですけど！
A high school tennis player is transported to a fantasy world where he is recognized as a hero. He quickly realizes that the world's standards of power are far below those of the high school tennis nationals in his original world. In this realm, tennis is the ultimate form of power, allowing him to strike down dragons or entire demon armies with a single shot. However, he soon discovers that the demon king is also a skilled tennis player.