Mr Hosokawa, 55, is the descendant of a long line of feudal lords and he likes to tout his aristocratic pedigree. Throughout the election campaign he cultivated an air of distant hauteur, as if the whole business of politics was beneath his dignity. He even pretended that he did not want the prime ministership, and that he only gave in to repeated requests from the other coalition members.
His image has been crafted to suggest, as his wife Kayoko repeatedly says in interviews, that he was born to be a leader, and that it is almost inevitable for him to have been made prime minister.
The photograph used on his election posters showed him in half-profile, smiling faintly and wearing a sweater, contrasting sharply with the stiff poses of his competitors, who stared straight at the camera and were dressed to a man in blue suits with white shirts and ties. Mr Hosokawa, the voter was led to believe, was the noble, disinterested outsider, finally called to lead his nation through a period of political confusion.
The truth is rather different. Mr Hosokawa has coveted the prime ministership, a post held by his grandfather half a century ago, ever since he entered politics in 1971. Some careful tactical calculations on his part, and an unexpected hiccup in the normally stable political system in Japan, have rewarded Mr Hosokawa's ambition with the glittering prize he has long sought.
But how long his seven-party coalition government will last, and what it will achieve, depends less on Mr Hosokawa's posed nonchalance than on the political wiles of a few powerful men behind him - notably Ichiro Ozawa of the Shinsei party - as they try to institute electoral reform and fend off the continuing challenge to the coalition from the LDP.
A significant shift has begun in Japanese politics, but Mr Hosokawa is more an elegant than a prime mover in the process. He comes from Kumamoto on the southern Japanese island of Kyushu. For centuries the Hosokawa clan ruled the area as a feudal fiefdom, and even today Mr Hosokawa is referred to by some as 'lord'.
His maternal grandfather, Fumimaro Konoe, was prime minister in the late 1930s and early 1940s, presiding over Japan's invasion of China and the creation of the Greater East Asian Co-prosperity Sphere policy. He committed suicide at the end of the war to avoid being tried as a war criminal.
After university the young Mr Hosokawa worked as a journalist with the liberal Asahi newspaper, before winning election to the Upper House of parliament in 1971. But from the beginning his political ambitions were clear.
Despite his current image of an outsider dedicated to political reform, Mr Hosokawa quickly joined the Tanaka faction in the old LDP, the faction that was most corrupt but also the quickest route to the top in politics. When Yohei Kono, recently elected as the new head of the LDP, set up a splinter faction of the party in 1976 to protest against corruption in the LDP, Mr Hosokawa rejected Mr Kono's invitation to join him. 'A big fish does not swim in small streams,' was Mr Hosokawa's curt rebuttal to Mr Kono's overtures.
In 1983 the 'big fish' returned to Kumamoto to become the prefectural governor, and began a fairly successful programme of attracting high-tech industries to what had been a predominantly poor, agricultural district. He served until 1991, when he came to Tokyo. He says that he did not want to continue for another term because long tenures tend to encourage corruption.
After setting up the Japan New Party last year, Mr Hosokawa ran in the elections on a platform of political reform. He won 35 seats, which gave him the swing vote in the competition for a parliamentary majority between the LDP and the anti-LDP coalition. During the election campaign Mr Hosokawa refused to declare his sympathies for either side.
After the elections, heapproached the LDP first with an offer of partnership. With a preliminary agreement with the LDP safely under his belt he turned to the opposition parties and made them an offer they could not refuse. He would switch to them, but his price was steep: he wanted to be prime minister.
The other coalition partners were so desperate to end the LDP's 38-year monopoly in government and for a taste of power of their own that they conceded; the self-styled 'big fish' was given the job.
Few politicians expect the new government to last particularly long, seeing its main function as implementing electoral and political funding reforms. But for Mr Hosokawa the moment was sweet, as he finally achieved his goal of becoming a latter- day 'lord'.
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