Seiko Ayase is a major supporting character of the manga series Dandadan. She is the grandmother of Momo Ayase. Despite being a grandmother, Seiko has the appearance of a slender woman in her prime. Seiko possesses long snow-white hair that she generally ties up in a large top knot, wears red rectangular glasses, and can be seen smoking at times. Seiko has a phlegmatic personality and a highly uncouth manner of speech. Seiko can also come off as being a bit immature and often acts unladylike.