Hideki Maniwa, who became a jockey with his father's belief that "horse racing is life" in his heart, is still an apprentice, but he is a man who has the soul of Asura to the extent that he challenges senior jockey Tadokoro to a serious match and wins. However, Hideki has always had difficulties, such as being seriously injured by falling from a horse during a race and experiencing a sad farewell to his beloved horse, Raijin Echo. On the other hand, at a stable in Hokkaido, a thoroughbred was born. Idaten King is a play on the name of the owner, Ida. Hideki, who has a fateful encounter with his beloved horse, pushes forward in the world of horse racing with horseman Masaru and Ida's daughter Reiko to fulfill his dream.