ケイト

A model and up-and-coming movie star, she transforms into the yellow bunny Seratonin using an earring and a compact. She is often "busy" with other jobs and tends to speak in a monotonous tone. When she transforms, she says "Come out, Seratonin!". A black-haired girl with a strange character, Kate also happens to be into the occult. She owns a crystal ball and makes tea using a chemistry set. Seratonin is the chemical in the brain which causes happiness.