Eris is a 16-year-old scout for the Catian people exploring Earth. Tall and well endowed, she has easily befriended many people, as well as regular cats she has met on Earth. Initially most do not believe her to be an alien, but she shows Kio the proof directly with her technology, ears, and tail. While she is learning the ways of Earth, she is also a competent fighter who employs strategies and technologies not seen on Earth. Her interactions with Kio are closer and more emotional, potentially due to the fact she is 16 and about to enter her first heat. With the kindness and interest he has shown, she has selected him as a mate. Eris was forced to take chemicals to end her first heat prematurely as it was causing disruption to her duties as an ambassador and representative of Catians on Earth, with high expectations for her second heat and another chance to mate with Kio. She develops feelings for Kio after she found out he risked his life to save her when she was captured. When Aoi admitted that she was jealous of her closeness to Kio, she eventually kisses him in the anime adaptation's final episode, after Eris says she would go with the Catian law that places no restriction on the number of lovers rather than earthling law that says a person can have only one mate, she did not bear any ill will towards her and is happy that somebody else shares the same feelings as she does.