Sonoko is a young woman with short, straight blue hair which goes down to her shoulders. She has light blue eyes and fair skin.
Not so much shown about Sonoko's personality, but she seems to be calm, collected and hardworking, and also matured, and even sometimes childish.
Sonoko is Utaha's editor. They both seem to trust each other and Utaha has never lied for her about her books. However they sometimes can argue about some small things. Sonoko calls Utaha for ''Shi-chan.''