The issue is that we have very little recourse for these types of situations. Obviously if someone stalks you, they will be arrested and dealt with. However, some people will then skirt around the whole stalking label by using loopholes. For example, in theory someone could follow you around, discreetly and make it convincing enough that any places you do run into them is common enough to support their case that they aren't stalking you. Now you could get a restraining order and that would be that but unlike the regular person, she would have to consistently get restraining orders then as multiple people will stalk her. It also doesnt help that Japan expects the victim to behave in a manner that is "appropriate" even in a bad situation.
Now we can all say the obvious "why can't people just be good and leave her alone?" Telling that to a bad person is pointless as they either are unaware of their action being bad or they simply don't care.