Nobody Knows - Hirokazu Koreeda

In Tokyo, the reckless single mother Keiko moves to a small apartment with her twelve years old son Akira Fukushima and hidden in the luggage, his siblings Shigeru and Yuki. Kyoko, another sibling arrives later by train. The children have different fathers and do not have schooling, but they have a happy life with their mother. When Keiko finds a new boyfriend, she leaves the children alone, giving some money to Akira and assigning him to take care of his siblings. When the money finishes, Akira manages to find means to survive with the youngsters without power supply, gas or water at home, and with the landlord asking for the rental.