Isumi is a black-haired girl who is always wearing a kimono. Another one of Nagi's close friends, she and Nagi met at a party a long time ago. When all the other children, Sakuya included, laughed at Nagi's first attempt at writing her own manga, Isumi took interest in it and asked Nagi how it ends; Nagi then asked Isumi (in a childish sense) to marry her. Like Nagi, Isumi is very rich. Unlike Nagi, Isumi is soft-spoken, kind, and can cook well. While she does not have an awful sense of direction, she constantly gets lost due to the fact that she is apt to forget her destination, though she is able to disappear from people's eyes instantaneously. She has feelings for Hayate and does not wish to see him sad.