All in favor of assigning custody of the child to her friend's parents say aye?
In seriousness though, she's technically right. There's a high chance she will be sent away to an orphanage under the guardianship of a child welfare center.....if no one else intervenes that is.
Laws have improved in Japan regarding child abuse, and parents can be held for criminal liability and stripped of custody. Rates of unsolved abuse are still very high as it's difficult in Japanese society to to pry into another's family affairs, whether you're a friend or a civil servant. That being said, it is now possible for a child welfare center to take over custody of a child more quickly and with less bureaucracy. If the MC and his parents move quickly, they could adopt her.