She is Shougo's sister and she takes time to teach the young children how to read and write. When she was just a child, she and Shougo were brought away from Japan to avoid the persecution of the Christians where their parents had died. Some time later, they met and rescued Shouzo, who fell for her. However, she had gotten their mother's sickness: tuberculosis. During the Shimabara Arc, Sayo and Sano fall in love. However, due to her deteriorating condition, things did not bode well. In the end, Santo shot his gun and Sayo sacrificed her life to save Elsten and died of a shot in Sano's arms.