Cooan was in love with Rubeus, and was ready to do anything for him, even if he brushed off her advances most of the time.

Cooan was tasked by Rubeus to capture the "Rabbit" Chibi Usa. Cooan failed in her mission due to Sailor Mars' intervention, and Rubeus gave her a bomb and told her to destroy everyone, including her "useless" self, with the explosion. Rubeus broke Cooan's heart by telling her he didn't do stupid things like loving somebody. Cooan lost the will to live and allowed herself to be trapped by the sailor soldiers, fighting like a mad woman. Sailor Mars took pity on her and asked everyone to stop attacking, and Sailor Moon used the Holy Silver Crystal to turn Cooan into a normal human being.

Cooan became a cosmetics sales lady after, and became close friends with Rei Hino / Sailor Mars.