"Uma Musume Pretty Derby" is set in a world where anthropomorphized racehorses, known as "horse girls," compete in races and idol competitions. These horse girls are inspired by real-life racehorses, blending their racing careers with idol activities. The story primarily revolves around Special Week, a cheerful and determined horse girl who moves to Tokyo to fulfill her promise to her mother, a legendary racer, to become the best in Japan. Special Week enrolls in Tracen Academy, a prestigious school where horse girls train to excel in both racing and entertainment.

At Tracen Academy, Special Week meets a diverse cast of characters, each with unique personalities and racing styles. Among them is Silence Suzuka, a reserved and talented horse girl who becomes Special Week's idol and rival. The two form a close bond, with Special Week striving to surpass Silence Suzuka while also supporting her. Other notable characters include Tokai Teio, a spirited and ambitious horse girl with a strong sense of justice; Mejiro McQueen, a calm and composed competitor with a regal demeanor; and Gold Ship, a mischievous and unpredictable racer who often disrupts the status quo.

The narrative explores the challenges and triumphs of the horse girls as they balance their dual careers. Racing competitions are intense, with the horse girls pushing their limits to achieve victory. The series delves into their personal struggles, such as overcoming injuries, dealing with rivalries, and maintaining their idol personas. Special Week's journey is marked by her unwavering determination and the support of her friends, as she works tirelessly to climb the ranks and earn the title of "Twinkle Series" champion.

The series also incorporates elements of teamwork, camaraderie, and personal growth. The horse girls train together, face setbacks, and celebrate their successes, creating a sense of community within Tracen Academy. The narrative highlights the importance of perseverance, friendship, and believing in oneself, as the characters navigate the competitive world of racing and entertainment.

"Uma Musume Pretty Derby" combines sports drama with idol culture, offering a unique blend of action, emotion, and character development. The story is driven by the aspirations and relationships of its cast, making it a compelling tale of ambition and camaraderie in a distinctive setting.