I live in Tokyo and follow the same rules for smoking. If there is a smoking ban on the street, I don't vape. If inside, I vape in the same area that smoking is allowed. The main thing, is that many people do not know what vamping is. But luckily, many bars and restaurants still allow smoking. Smoking in the streets in unadvisedly and illegal in many areas.
Japan is a country of humility, think about how others would think. Don't force the issue, be polite and just understand that it is considered smoking. Find smoke friendly places to vape.