Kokoro's mother is a middle-aged woman who is the only known parent of Kokoro Kosaka. The whereabouts of Kokoro's father are unknown, and we never find out if Kokoro's mother is or has been married. She is the babysitter of Kokoro's relative Emi and is first seen in chapter 7 of Wallaby in which Emi's visiting the house and Kokoro's mother grants her permission to take Wallaby to her house, since Kokoro's mother did not think that a stuffed animal would mean so much to her daughter, a high schooler. Physically, she resembles Kokoro, having practically the same hair colour and skin tone. Kokoro's mother also helps her daughter retrieve Wallaby by telling her that she gave it to Emi, even if this makes Kokoro angry at first.