Be Polite When Using Mobile Phones In Public
Privacy is held in high regard in Japan. And as such, this includes having conversations on mobile phones. If you happen to receive a call in public, there is an expectation to maintain a basic level of privacy. Could you imagine this being a standard in the US?
If you should find yourself in this situation, it is preferred that you speak in a calm and low voice. It is expressly forbidden to take calls on speakerphone, as this is uber disrespectful. These kinds of acts are frowned upon by passersby. It almost seems like the best kind of public shaming possible.