Sumire appears as a small toddler, with messy black hair tied back with a pink bow. She has extremely large black eyes that fade to pink with white pupils, a trait common among the Kamado family.
She wears a grid-patterned pale purple kimono with a light pink obi and has no footwear.
Being a toddler, Sumire is usually happy and cheerful, always shown smiling. Being very young, she is curious, as shown when she approaches Yoriichi talking with her father and later watched him perform the moves of his Sun Breathing. According to Sumiyoshi, Sumire enjoys being lifted up and she squeals with joy when Yoriichi picks her up, since Yoriichi is much taller than Sumiyoshi. Despite her happy-go-lucky demeanour, she appears saddened when Yoriichi leaves them for the last time.
As Tanjiro loses consciousness amidst the final battle against Muzan, he awakens amongst the memories of his ancestor Sumiyoshi. While he and Sumire stand outside their home, she notices Yoriichu Tsugikuni nearby standing under a tree and tugs at her father's clothes to inform him. After a long chat, where Yoriichi tells Sumiyoshi about his life and his regrets about Muzan's escape, the moment grows gloomy; Yoriichi becomes despondent after reminiscing on his tragedies and Sumiyoshi cannot find ways to cheer him up. At that moment, Sumire appears. Tugging at the demon slayer's haori, she asks him to carry her. Yoriichi oblidges at his friend's request, noting she enjoys it greatly. As Yoriichi lifts her up, she becomes overjoyed. Her laughter causes him to break down in tears and he hugs the little girl. Though somewhat bewildered, Sumire returns the favour and embraces him too. Her mother appears shortly after and cheers Yoriichi up as well.
Some time later, Sumire offers Yoriichi a flower as a gift. While in her mother's arms, she watches Yoriichi perform the Sun Breathing's forms in a show at her mother's request, smiling at the end.
As a normal human, Sumire doesn't perform any supernatural powers.
- Much like how Sumiyoshi bears a resemblance to Tanjiro, Sumire bears a shocking resemblance in appearance to Nezuko Kamado along with her own mother Suyako.