In a world very much like our own, great race horses of the past have a chance to be reborn as "horse girls"—girls with the ears and tails of horses as well as their speed and endurance. The best of these horse girls go to train at Tokyo's Tracen Academy, hopefully moving on to fame and fortune as both racers and idols.
Special Week, a high school horse girl from the countryside, has just transferred to Tracen, and she's determined to fulfill her promise to her mother to become the best horse girl in Japan. On her way to school, she takes a pit stop at the race track and instantly falls in love with Silence Suzuka's style, becoming determined to race on the same team as her.
Since childhood, horse girls Kitasan Black and Satono Diamond have admired and aspired to be like their fellow horse girl named Toukai Teiou. Chasing their dreams, they enroll in Tracen Academy, an institution dedicated to training horse girls and preparing them for legendary races. Soon after, Kitasan Black lands on Team Spica, the same team as Teiou. Beaming with motivation, she remains undefeated until she fails to win her first Grade 1 (G1) race—the most prestigious type of race in the league—but she is determined to unleash her true potential as a horse girl.
Meanwhile, Satono Diamond comes from a long line of horse girls who, despite sporting incredible running prowess, have never won a G1 race. It is up to her to finally break this curse and bring the Satono clan the glory it deserves.