Nobody Knows (2004)

"The family that recently moved into the apartment is mother Keiko (played by You) with four children: Ming (played by Yuya Yanagira), Kyoko, Shigeru, and Yuki. But the mother had to lie to people around her, saying that her husband was working overseas and that she and her eldest son were living together. The fact is that the other three siblings are "black children" because the four children..."