Any accident (damage to aircraft) or incident where anyone is injured (spends more than 48...or 72...hours in hospital) results in it becoming a police matter.
Case in point. Last year a B737 was on descent into Fukuoka (no, there's no "c" in that word!!), and the aircraft encountered CAT.
One of the cabin crew was injured, and it was thought that she would have to deadhead back to home base, due to her inability to work.
I was due to take over the aircraft, however was told that the flight was now delayed - time frame unknown - as the police had to "inspect" the cockpit, and that nothing was allowed to be touched!!
Remember, the accident occurred on descent, and so the aircraft would have had to have been configured for landing, and then subsequently after landing and then parked, re-configured again.
However, "the scene of the crime" was not to be disturbed, and the oncoming crew (us) were not allowed near it.
Fortunately, the F/A underwent a miraculous recovery - no doubt after a lot of pressure was applied to her, as to exactly what the repercussions of her injuries would mean on the cockpit crew - and she elected to continue duty.
The investigation was cancelled.
THAT is the mentality here.
Japan is a Police state, where everything, and everyone is very closely monitored. And THAT is one reason why Japanese don't usually stand out in a crowd.
"
Does this apply to Western pilots on Contract????"
Without a doubt!!