Depends on whether this was a simple fracture, or something more complicated. I'm sure a doctor on board evaluated the passenger and determined it was safe to proceed.

The passenger may also have been pretty vocal about his/her preference to land in Tokyo and get proper care than landing in a smaller city or more remote location for spottier healthcare and no easy way back to Tokyo or the USA. I for one, if I was in a bearable amount of pain with some Tylenol, would suffer through to Tokyo for these reasons.

Hope everyone recovers quickly!