Shizuka is Shizuru's younger sister, who is not mentioned many times.
Appearance
Shizuka probably looks similar to Shizuru when she was a child, though it is not said she does resemble her. Even though they are related siblings, it is almost certain that Shizuka does not have heterochromia, since Shizuru recieved the golden like eye coincidentally as a consequence for healing her family.
What Shizuka may look con-substantial to.
Personality
She is only heard speaking twice in the entire story, words make it seem that she has a sunny and upbeat personality in contrast to her sister's shy demeanor.
Synopsis
Shizuru's Past: Shizuka was born some time after Shizuru accidently erased her parents memories of herself in order to stop them from fighting. Her appearance is not seen, but her voice is heard when Shizuru and Kotarou visit Shizuru's past home.
Shizuru's Route: She is heard at the end of the route where she calls to her mother and then they both vanish from the the Key's salvation.
Harvest Festa: She and Shizuru know each other and are close sisters.
Trivia
- Her name may be a reflection of her parents retaining some of their memory of Shizuru.