Culturally speaking, Japan is by most aspects the opposite of France and this also goes for the anti-tobacco policy. In France, smoking is forbidden in inside areas but allowed outside, whereas Japan does it almost the opposite way.
I say "almost" because not all outside areas are non-smoking, and not all inside areas are smoking areas. For instance, it is forbidden to smoke in places such as shops, librairies, public offices etc. On the other hand, most bars and restaurants allow it and do not even have separated areas.
Outside however, it's just about the opposite and this symbol is often displayed on the sidewalks:
It of course indicates that the sidewalk is non-smoking. I think most of them are, although I'm not completely sure about that.
Anyway, apart from the cultural differences, I don't really understand the reason behind that system. Indeed as a non-smoker, it is much easier for me to avoid other people's smoke outside than in restaurants. So why not just do the opposite, allowing people to smoke outside but not in restaurants? It just seems to make more sense that way.
Besides, the way Japan leads their anti-tobacco campaign is a little weird to say the least. While in France and many other countries, the dangers of smoking are clearly pointed out through striking messages and sometimes shocking pictures, here they insist on the nuisance towards non-smokers. Which is not a non-sense in theory, but they do it through illustrations that are completely ineffective. At least they are funny and definitely popular among foreigners, although I suspect that it wasn't the intended purpose. Here are some samples, enjoy:
Category: Everyday life