Uma Musume: Cinderella Gray is a spin-off title of the Uma Musume project by Cygames. It follows Oguri Cap through her time at Kasamatsu Training Center Academy and on her journey of becoming a legendary horse girl. (from Mangaupdate)

A girl with grey hair appears in the desolate land of Kasamatsu. The girl, who would later be called a "monster," is on a quest to find out where she is going... From rural to the legends of central Japan. A coming-of-age Cinderella story starts now! ( Translated with DeepL from official Cygames amazon store)