Daughter seen while younger before the timeskip, probably 3 here.
Seen older, after 2 years have passed with Ryner in prison, she is probably 5 here.
The supervisor's daughter or warden's daughter is the daughter of the supervisor and the supervisor's wife. He exclaims in conversation with Ryner that she's only 3 years old, though she appears older when Ryner gets out.
She calls out to Ryner by name. It is unclear if she's ever seen him, but since Ryner appears to be the only prisoner in the jail, it is likely the guard may have told his family about the prisoner and his name, so she figured out who he was.
She is voiced by Mami Fujita.