Which of Misaki Watari's qualities make her a perfect fit for her role as Kafuku's personal driver?

As time goes on and Kafuku becomes comfortable with Misaki Watari's presence, he begins to appreciate particular characteristics within her understated personality. Kafuku states that he can be screaming his lines on the seat beside her, but that she always remains unfazed and acts as if she hears nothing as she focuses solely on the task of driving. In addition to these qualities, the narrator also states that while Kafuku cannot tell how Misaki Watari feels about him as a person, he does not care that much about how she feels about him since "He liked her smooth and assured driving, her lack of chatter, and the way she kept her feelings to herself" (13).