18 Years of "Imprisonment"

Today it was exposed that a 40-year-old mother had "imprisoned" her developmentally-challenged daughter in her apartment for 18 years since she was born... People from school and city hall had tried to contact the family before, but they never saw the girl nor stepped inside her house. Her mother was reported to say that she was ashamed of her daughter's disability...

I understand that it is tricky to decide how much power the State should have in intervening "private" affairs of the family. But I think governmental actors in Japan tend to shy away too much from getting inside the family when some threat to human and legal rights is suspected.