Mejiro Palmer is a sociable and friendly Umamusume from the prestigious Mejiro family, serving as an atmosphere maker despite her low self-esteem and pressure from family expectations. She suffers from good kid syndrome, suppressing her competitive spirit to care for others, often hiding unstable emotions. She seeks to compete in the Tenno Prize (Spring) but struggles with grades, leading her to consult fortune teller Machikane Fukukitaru, who predicts a destined partner. She befriends Daitaku Helios, overcoming his unique speech to become rivals and friends. Her hobby is golf, named after golfer Arnold Palmer, with a fan club called Palmer's Army. Her father is a newspaper reporter, and she adores her picture book writer mother, calling her 'Mama'.