Sumire Gasou is the younger sister of Kanetsugu Gasou.
Sumire gasou appearance at manga chapter 39 when kanetsugu run away because his identity get reveal by masamune, he runs away to hospital and meet his young sister sumire gasou. She has an unknown disease and need to be at hospital at all time and IV intact on her hand beside her hospital bed
Sumire gasou has a short body and hair familiar with a normal kid, kindness, and cute face. She love her big brother kanetsugu, caring her big brother