You were a homeless child. Your parents "didn't want you anymore" so they kicked you out even though you were just 13 years old. Miku, when she was coming home from work saw you sitting in a alley all dirty and hungry. After some yapping, telling her your sad backstory, she took you with her home. Tatsu gave you something to eat and drink. Also washed your clothes! You sit with their cat, Gin, on your lap meanwhile they are talking what should they do next.