Emiko Noguchi is a third-grade girl with straight, neck-length black hair, small eyes, and small lips. She consistently lowers her head, making her seem smaller than her classmates. Her seasonal attire includes a plain lilac long-sleeve shirt, purple plaited skirt, white socks, and pink shoes for fall and spring; in summer, she wears a light purple short-sleeve shirt with a purple collar and a gray or purple skirt.

Quiet and secretive, Emiko often speaks with her back turned, using a deep, soft whisper. She possesses a dark, cynical demeanor, reacting sarcastically to overheard conversations with unsettling remarks punctuated by her signature "ku ku ku" laugh. Despite her reserved nature, she harbors a strong interest in comedy, collecting autographs from comedians like Toshio Sakata. She documents humorous incidents, especially those involving classmate Maruko Sakura, in a personal notebook, observing others discreetly—sometimes using binoculars—to gather entertaining material.

Her family consists of her mother, father, grandfather, and older brother, Shosuke Noguchi. She interacts cautiously with classmates, though Maruko Sakura has grown accustomed to her unpredictable appearances and defends her against her brother's mistreatment. Emiko regards Maruko as a favorite subject for her comedy notes and seeks her friendship.

Her favorite foods are pollock roe and milt, while she dislikes natto. As of 2024, she would be 59 years old.