Marcia Saotome is one of three wealthy sisters running their family's fashion empire, actively selecting designs for production and sale. She attends school with her sisters and is renowned as a top athlete there, while also demonstrating sharp business skills managing the family company.

She possesses silver hair, green eyes, and brown skin. Marcia typically wears her school uniform or gym clothes but adopts other fashions outside school. Transforming into her heroic alter ego, Otomet Magenta, changes her outfit to include a helmet embedded with a magenta meteorite, a suit combining white, black, and magenta, and a bifurcated cape.

Personality-wise, Marcia can be smug, especially in family business dealings, yet shows a willingness to help others as a hero. Her relationship with the Mishina sisters is generally contentious, though they unite against shared threats, particularly those involving Yamato Shirai. Marcia harbors longstanding romantic feelings for Yamato, fueling her protective actions even at personal risk.

As Otomet Magenta, her capabilities exceed the Musumet team in specific areas: she exhibits greater raw physical strength than Musumet Red and operates at speeds surpassing Musumet Red's outside final transformations. Her powers derive from a magenta-colored meteorite, aligning her with the Otomet group, thematically representing the CMYK color model used in print—contrasting with the Musumet team's RGB motif associated with digital displays.

Within her family, Marcia maintains supportive relationships with both older sister Shion and younger sister Kou, collaborating in business and heroics. She places significant trust in their butler, George, turning to him for support.