Quite a welcome to his new job. At a press conference on Friday to try to assert his authority and reassure his critics, Mr Murayama acknowledged that there were worries about his government, but said: 'My job is to do my best to get rid of these worries.' Then he added: 'I am the supreme commander.' The pathetic thing is that no one, at home or abroad, is ready to believe him.
According to an poll yesterday, 44 per cent of Japanese disapprove of Mr Murayama as their prime minister, compared to 37 per cent who approve of him. The last two prime ministers, Morihiro Hosokawa and Tsutomu Hata, had approval ratings of about 80 and 60 per cent respectively.
An even smaller percentage - 29 per cent - of respondents to the poll, conducted by the Yomiuri newspaper, approved of the bizarre coalition of the Socialists and the conservative Liberal Democratic Party (LDP) that put Mr Murayama into power. The two parties, for four decades bitter rivals on either side of the Cold War fence, joined hands last Wednesday only to block political reforms pioneered by the last government. 'Marriage of convenience', 'adhesive-tape government' and similar negative epithets have been used by the press to describe what many regard as a spectacularly cynical political manoeuvre.
But when the laughter stops, foreign governments must return to the fact that Japan is the world's second largest economy, has the largest aid budget and the largest trade surplus, and is simply too important to confine to a comic film studio for the duration of its weird political antics.
In a week's time, the other leaders of the Group of Seven nations will be meeting Mr Murayama in Naples. Who is he? What does he stand for? And will his Socialist Party try significantly to change Japanese policies?
Born in Oita prefecture, on the southern island of Kyushu, Mr Murayama became a labour leader before running for office in the local assembly. In 1972 he won a seat in the Diet (parliament), and since then has been on the left wing of the Socialist Party.
He put most of his energy into pension, welfare and labour issues during his time in the opposition. But he argued vociferously against the dispatch of Japanese peace-keeping troops to Cambodia in 1992.
He was one of the organisers of his party's protest against the peace-keeping bill in the Diet, when he and his colleagues delayed the vote with the infamous ox-walk, in which each deputy spent some 30 minutes walking from their seat to the voting box at the front of the house.
Japan's Socialist Party is a strange creature, hardly comparable with European Socialist parties grounded in working-class support.
The LDP delivered economic growth year after year for four decades, and was therefore guaranteed the majority of working-class votes. The Socialists were thus relegated to being a party of protest, and could develop extreme policies, confident that they would never attain power to implement them.
But now they have suddenly attained power, their support for North Korea, opposition to the Japan-US security treaty and other such policies have evaporated like vampires at dawn. Within 30 minutes during his news conference, Mr Murayama reversed 40 years of Socialist Party policies, and promised his party would act like the conservative parties that have ruled up to now.
'The word 'socialism' does not appear at all in our party platform,' said the lifelong Socialist.