In the rural and desolate Kasamatsu Tracen Academy, a place far removed from the bright lights of central Japanese horse racing, a young horse girl named Oguri Cap trains with an unconventional and powerful running style. Discovered by a down-on-his-luck trainer, Jou Kitahara, Oguri possesses raw, untamed speed and a quiet, almost stoic demeanor, finding joy only in the simple act of running. Her gray, or ashen, coat sets her apart, and a deep-seated superstition in the racing world holds that gray horse girls cannot reach the highest levels of the sport. Despite this, Kitahara sees in her the potential to fulfill his own dashed dreams of glory.

The story follows Oguri’s journey from a no-name regional competitor to a national legend. Her initial races pit her against the disciplined and proud local ace, Fujimasa March. This rivalry ignites a competitive spark in Oguri, transforming her aimless passion into a determined ambition to win. After proving herself in regional events like the Junior Crown, she is scouted to transfer to the prestigious Central Tracen Academy in Tokyo, the heart of the horse racing world. This transition marks a major turning point, separating her from her first trainer and introducing a new, more technical mentor, Musaka.

The central narrative arc of the first season builds toward a clash with Tamamo Cross, another immensely talented gray horse girl who dominates the national stage. Unlike Oguri’s grounded, low-to-the-ground running style, Tamamo Cross is a flamboyant and powerful front-runner. Their rivalry becomes the emotional core of the series, as both carry the weight of proving that their ashen coats are not a curse but a mark of a potential champion. Their much-anticipated confrontation in the fall Tenno Sho, a race to determine Japan's best, serves as the climactic finale of the first part of the series, pushing both rivals beyond their limits.

Other notable narrative arcs include Oguri’s struggle to adapt to the high-pressure environment of Central Tracen, her desperate attempt to qualify for the prestigious Japanese Derby after a registration mishap, and her first foray into international competition in the Japan Cup during the second cour. The series is structured in two parts, with the first cour concluding on the intense rivalry with Tamamo Cross, and the second cour expanding the world to include powerful overseas challengers and new rivals like Super Creek and Inari One. Throughout, the story balances intense, stylized racing sequences with quieter character moments, exploring themes of perseverance, the burden of expectation, and the bittersweet cost of chasing greatness.