Kaoru Sasaki is a supporting character who works as a secretary in the dictionary editorial department at the Genbu Publishing company. She is a contract worker and a constant presence in the office, providing essential administrative support throughout the long process of creating the new dictionary, Daitokai. Physically, she is an adult woman with black hair typically tied back in a ponytail, which reaches her chest, and she wears glasses.

Other members of the editorial team refer to her as the super madam of the department, a nickname that suggests she is a seasoned, capable, and perhaps no-nonsense figure within the workspace. Her personality is not extensively explored in the narrative, but her steady and reliable presence implies a practical and professional demeanor, contrasting with the more eccentric or passionate personalities of her colleagues like Mitsuya Majime or Masashi Nishioka. She is an integral part of the team that unites to face the numerous challenges in publishing Daitokai, such as combating rumors of its cancellation and managing the intense workload of the final phases of compilation.

No specific information regarding her personal background, individual motivations for working on dictionaries, character development over the course of the series, or notable abilities beyond her role as a secretary is available. Her key relationships are primarily professional, working alongside the core editorial staff including Majime, Nishioka, veteran editor Kohei Araki, and the linguistics professor Tomosuke Matsumoto.