Gate In!

Fuyune, Akine, and Natsune. A new racehorse is born on the ranch of these three sisters who love horse racing and racehorses. They name the horse "Shikiou," and the three sisters dream of having him win the Japan Derby. Time passes, and Fuyune has become a trainer, Akine has become a ranch manager, and Natsune has become a jockey, all pursuing the dream they have entrusted to her beloved horse. However, Shikiou himself has been living a life of obscurity as a racehorse who has given up on winning... It's the start of a horse racing story where these three sisters pursue their dream head on!!

(Source: Kadokawa, translated)