Upholding "fraternalism" as his personal political banner, Yukio Hatoyama has often been called an "alien" in the political jungle but has arguably grown more capable as a leader in recent years.
Now he is all but certain to become the prime minister when the Diet next convenes after his Democratic Party of Japan secured a landslide victory in Sunday's House of Representatives election.
A "soft-shell" liberal and thoroughbred from a blue-blooded political family, Hatoyama, 62, is one of the founding members of the DPJ, which was launched in 1996. He headed the party between 1999 and 2002, regaining the post last May.
His political credo of "yuai" (fraternalism) comes from his grandfather. But it is an unfamiliar term to most people, and his behavior has been considered bizarre at times. But his steadiness during the three years he served as secretary general under Ichiro Ozawa helped him return to the DPJ's helm as a self-avowed "mature Hatoyama," humbled, chastened and cured of his past indecisiveness.
A graduate of the University of Tokyo's Faculty of Engineering, Hatoyama turned to politics in 1986, entering the House of Representatives with the Liberal Democratic Party before bolting in 1993 to form the now-defunct New Party Sakigake.