JUNICHIRO KOIZUMI was a tough act to follow. The former Japanese prime minister, who stepped down a year ago this month, swung into office in April 2001 like a wrecking ball, pledging to “destroy” his ruling Liberal Democratic Party (LDP) if it didn’t accept free-market reforms and seeking to cripple the LDP faction system. With long silver locks and a zest for American pop culture, Koizumi cut a far more dashing figure than most Japanese leaders. In foreign affairs, he lived up to his self-billing as a “diehard pro-American,” deploying naval vessels for the war in Afghanistan and later sending several hundred noncombat ground troops to aid the reconstruction of Iraq.