Eiko is a fellow actress of Chiyoko's that is jealous of her youth.

Spoiler

Flashbacks reveal that Eiko plotted to rid her films of Chiyoko from the start upon seeing the height of Chiyoko's talent. At first this works, and Chiyoko drops out of her first movie to follow the man she had met back home. Chiyoko returns to films, however, and Eiko finally steals Chiyoko's key out of hopes that Chiyoko will lose her drive to continue movies.