When buying a property in Japan non-residents have to provide a Statutory Declaration as proof of address and signature to get the title transfer accepted by the Tokyo title registration office. This declaration is a notarized document stating the name, address and signature of the buyer. Here is a template.
Normally the buyer can just go to a local notary public to get this document notarized. However the Tokyo registration office refuses to accept a document that is not notarized by a legal representative of country of citizenship. As the template Statutory Declaration does not mention the citizenship of the buyer, this is often overlooked. However if you are not living in the country of your citizenship it is recommended to get it notarized by your embassy in your country of residence to make sure it is accepted. To complicate matters further consulates of Commonwealth countries in other Commonwealth countries (for example the British consulate in Singapore) do not provide notarial services as these countries recognize each other's notaries. And not all countries have embassies or consulates everywhere. In such cases we need to request a special exception from the Tokyo registration office to get an SD excepted.
For residents of Hong Kong there is a free public service where they can perform a notarization within 30 minutes.