Operator 21O (pronounced Operator two-one-oh) is an android communication operator permanently stationed at the “Bunker”. Her duties include sending directives to the YoRHa soldiers on the field as well as information analysis. Personalities slightly differ between units. Operator 21O, responsible for YoRHa No.9 Type S, is level-headed, cold, and impersonal. She shuns 9S's attempts at casual conversation and does not pay heed to his compliments of her. In terms of personality, she is a polar opposite to the much more outgoing Operator 6O.