This isn't exactly true anymore, though some inertia still remains on the part of authorities to intervene in family affairs. Police have been given the legal authority to act solely and immediately on the recommendation of CPS before any additional investigation, since a few years ago. The bigger problem lies with CPS, where a lot of centers are understaffed and employ officers who are not properly trained. The changes in the laws were accompanied by new operating guidelines and funding for CPS, but this has not fully solved those issues even today.
In fact child abuse statistics have risen, though if one peels below the surface, this may actually be a sign of things starting to work. A lot of child abuse cases simply went untracked....even if authorities knew about it. The rise now is due to these cases actually getting reported, and more importantly, solved.
True about the girl not wanting to be sent away though. If her parents are exposed, she will likely be sent to an orphanage. In fact a huge proportion of kids in Japanese orphanages aren't actually "orphans", they're victims of abandonment or abuse like her. There are only a few which accept minors of her age, so she will likely be sent pretty far away.
