Wonder if they have ability to organise ground handling as a contingency at NRT. Get the pax and bags off at least, people can get on with their holiday/onward travels. Yes an inconvenience but not insurmountable.
Thinking about it a little bit, the "best" scenario may be (assuming crew hours available) to outright cancel VA78 tonight ex-HND, have crew positioned over to NRT to ferry empty back to CNS.
-8IA is scheduled to fly BNE-CNS tomorrow morning anyway, that can turn in to VA77 to HND and -8IC pick up (late) the rest of the day ex-CNS that -8IA was meant to do. Or just turn -8IC back to HND/leave in Japan overnight and cancel VA78, and VA77 tomorrow.