After her family had been killed by Demons, Sumi was taken in by the Butterfly Mansion. Like the other members of the trio, she is very bright, cheery, and helpful. She is portrayed as more polite and mature than what is usually expected for girls her age.She sports a long-sleeved nurse uniform tied with a blue ribbon around her waist and wears white socks and shoes.Sumi has light skin and a set of black, button-like eyes. She wears her hair in low pigtails fastened with blue butterfly clips.