A young, hip mother moves with her twelve-year-old son Akira to a flat in Tokyo. When the suitcases are inside and opened, three more children roll out. They each have a different father and have never been to school. No one knows of their existence, so the three youngest are forbidden to leave the flat, make noise or come out onto the balcony during the day. One day, their mother disappears. She leaves some money and a note asking the eldest child to take care of his brother and sisters. With a twelve-year-old as their father, the children initially manage to come to terms with their lives. Until the money runs out.
Based on true events, Nobody Knows caused a stir in Japan.