Ruby Daiichi is a fictional Uma Musume character associated with the Uma Musume: Pretty Derby franchise. She is portrayed as a horse girl competitor and idol-like trainee within the series' racing and school-life setting. As part of the cast, she contributes to the story’s ensemble of aspiring racers, each pursuing victory, growth, and personal dreams. Her role centers on training, competition, and the emotional bonds between teammates and rivals in the world of horse racing entertainment.