The death of a 3-year-old girl, thrown into a river by her mother in November, underscores shortcomings in the nation's child protection system, 10 years after amendments to the child welfare law purported to fix it.

Ayumi Sato, of Tsubame, Niigata Prefecture, had sought help with raising her daughter, complaining of the toddler's demands.

Weeks later, on Nov. 19, Miyu Sato's body was found floating in the river. Ayumi said she had dropped the girl from a bridge.