Note that the Prime Minister in Japan is not 'elected' via direct vote, like the US President, but rather becomes Prime Minister when he/she is made leader of the Party that is in power (has the majority of seats) in the parliament, or in the case of Japan, "the Diet".
So, it's all over except for the formality. Perhaps a US parallel is that the winner of the presidential election in November is the 'President-Elect', but not the President until sworn in in January.
Note that the Prime Minister in Japan is not 'elected' via direct vote, like the US President, but rather becomes Prime Minister when he/she is made leader of the Party that is in power (has the majority of seats) in the parliament, or in the case of Japan, "the Diet".
So, it's all over except for the formality. Perhaps a US parallel is that the winner of the presidential election in November is the 'President-Elect', but not the President until sworn in in January.