Who is Sachi from The Samurai's Garden and what is their importance?

Sachi was a young woman when she discovered that she had leprosy. Sachi tells Stephen that she was a spoiled, beautiful young girl, and that she felt nothing could possibly tarnish her future. She was best friends with Matsu's little sister and betrothed to Matsu's best friend, Kenzo, when the leprosy rash developed. It was then that Sachi went to Matsu, asking what she should do. Sachi tells Stephen that she had brought dishonor to her family by contracting the disease and that she planned to join several others in suicide on a particular morning to restore her family's honor.