She is a young 13 yearold girl 14 after episode 4 abandoned by her mother and a victim of sexual abuse by her stepfather. She has run away from home and is homeless at the start of the series subsisting on bread crusts she is given at a local bakery under the pretence that they are for the small puppy that accompanies her. She found and named the puppy Wanta. She ends up living with Kohta and Yuka as her legal guardians. Mayu befriends Nana and tries to take her under her wing. Source: Wikipedia