I wouldn't count on there being much, if any, consumer protection of any kind in Japan, especially for non-Japanese.

On my last trip to Japan, travel home was interrupted by a typhoon. United and other American carriers did their best (and usually succeeded) to protect people who booked through them, even if the actual booked flight was on Japanese carriers. ANA, the one we had tickets booked on, completely abandoned us, never volunteered any info, and were 100% unhelpful. I don't know about other foreign carriers, but I certainly wouldn't expect ANY help from the Japan side.