The Story Behind Uma Musume’s Most Famous Rivals

Kitasan Black and Satono Diamond Soft Acrylic Keychain from Uma Musume Pretty Derby

What This Item Is

This is a circular soft acrylic keychain featuring Kitasan Black and Satono Diamond from Uma Musume Pretty Derby. Character artwork is printed on a round acrylic disc, connected to a silver lobster-claw swivel clasp via a jump ring — a construction that has become standard across Japan’s anime and game merchandise market. The keychain arrives heat-sealed in a transparent OPP bag and appears to be unopened, though buyers should confirm condition directly with the seller. A copyright marking of © 2021 UPD2AP confirms manufacture in 2021 or later, placing this item within the wave of licensed goods that accompanied Uma Musume’s mobile game launch that same year.

The Franchise and the Real Racehorses It Celebrates

Uma Musume Pretty Derby is a media-mix franchise developed by Cygames. Its core premise transforms real Japanese racehorses into anime characters — depicted as girls with horse ears and tails — and builds storylines around their actual racing careers. The franchise spans three TV anime seasons (2018, 2021, and 2023), as well as manga, music, and a mobile game released for iOS and Android on February 24, 2021. That game topped App Store and Google Play sales charts in Japan within weeks of launch.

Kitasan Black is based on the real horse born in 2012, who won seven Grade I races — including two editions of the Tenno Sho (Spring), the Tenno Sho (Autumn), the Arima Kinen, the Takarazuka Kinen, and the Kikka Sho — and was named JRA Horse of the Year in 2017. He was famously co-owned by singer Saburo Kitajima. In the Uma Musume anime, he is the protagonist of Season 3, which aired in late 2023, significantly raising his recognition among international fans. His character has black hair with white highlights — reflecting the horse’s blaze and stripe markings — and red eyes.

Satono Diamond is based on the 2013-born racehorse owned by Osamu Satomi of Sega Sammy Holdings. The horse won two Grade I races, among them the Kikka Sho, and famously defeated Kitasan Black at the 2016 Arima Kinen. The two horses met across multiple major races during their careers, forming a genuine on-track rivalry that the Uma Musume franchise has carried directly into its storytelling. Satono Diamond’s character has light purple hair and brown eyes.

Why These Two Are Consistently Paired

The acrylic keychain — known colloquially in Japan as an “acruki” — has been one of the most common formats in anime and game merchandise since the 2010s. Circular designs in particular suit serialized character collections, sized and shaped so that fans can gather an entire cast over time. These goods circulate through specialty retailers such as Animate and Gamers, at events like Comic Market and AnimeJapan, and through official online storefronts.

The Kitasan Black and Satono Diamond pairing appears repeatedly on Uma Musume merchandise because their rivalry carries real narrative weight — both within the franchise and in the actual racing record. For fans who know the horses’ histories, the pair represents a documented chapter of Japanese racing, not just fictional drama. Since the Season 3 anime foregrounded Kitasan Black as its lead, international interest in goods featuring this character has grown noticeably, particularly among fans in East Asia and the wider global anime community.