I doubt it is hardware related, which means the game has been corrupted.
You can file a bug report following the procedures in the sticky thread on the subject.
Now, as to what you can do about it that is tricky.
Maybe nothing, maybe using an earlier save.
One thing you can try is Loading the save as a different small nation in say South america.
Play past the point that it crashes or say let some time run at least till after the death notice.
Then save the game under a new name, reload that as Japan and see if you can continue.
You can file a bug report following the procedures in the sticky thread on the subject.
Now, as to what you can do about it that is tricky.
Maybe nothing, maybe using an earlier save.
One thing you can try is Loading the save as a different small nation in say South america.
Play past the point that it crashes or say let some time run at least till after the death notice.
Then save the game under a new name, reload that as Japan and see if you can continue.