Sōsuke! Look at me! My mother made me a new dress! Isn't it pretty?
- —Kumiko to Sōsuke
Kumiko is a friend of Sōsuke and a student at Himawari Nursery School.
In film
Kumiko greets Sōsuke at the nursery school where she shows him her new dress. Another classmate comes up to him and asks him to play, however, he states that he is busy. Kumiko argues, stating he is too young to be busy, and walks away with the words, "You're so weird!"
Kumiko sobbing.
Sōsuke then goes outside to check on Ponyo who he is holding in a bucket. Kumiko shows up behind him and tells him he is not allowed to bring things to school, to which he replies that he is not taking it on school grounds and tries to hide Ponyo in the bushes. She then peeks over and sees Ponyo, telling Sōsuke to let her see. He reluctantly agrees after she has promised to not tell anyone about Ponyo. Upon seeing Kumiko, Ponyo snobbishly turns from her direction. Kumiko gets angry at this and begins to comment on Ponyo's unusual appearance, which results in Ponyo spraying a stream of water all over Kumiko, soaking her new dress. Kumiko begins to sob heavily and Sōsuke sees this as a chance to escape.