A TERRIBLE generality here, but here goes: believe me, Japanese "reflexes" are frequently very very slow in emergency situations. Everything is usually just so peaceful and quiet and low key in life in Japan, and people do not expect sudden happenings, that they are frozen and just observe when some situation does break out. Hence a guy can end up stabbing 10 people before being disarmed, whereas all kinds of Americans would be tackling or throwing things at such a person to disable him, even if he were armed with a revolver. In Japan, a terribly over-analytical nature and people in general. Good hearts, but pondering a little too deeply trying to make sense of suddenly changing things, when one's fundamental instinctual nature (such as in the case of the Good Canadian) should kick in. I myself have "sprung into action" on a number of occasions here; only to be bewildered by those around me staring and doing nothing and coming around to the reality a good minute or two after me, the Westerner.
They may have also thought she was committing suicide, and did not want to get "involved" because to have done so would have placed them at a police box for several hours helping on forms and eyewitness reports, and heaven knows, "work (and those at work) is waiting."
Sad sometimes.