From Asia Times (link):
With no sign of a thaw in chilly relations with Tokyo, Beijing appears to be isolating Japanese Prime Minister Junichiro Koizumi in a bid to discredit him and his policies.
This shift in China’s Japan strategy has become increasingly evident in recent weeks and is expected to translate further into action leading up to Koizumi’s exit from the political stage in September. He is to step down as president of the ruling Liberal Democratic Party (LDP), and thereby as prime minister.
The message Beijing apparently wants to get across is: without Koizumi, Sino-Japanese relations would have flourished, and whoever succeeds him in the autumn has a good chance of turning liabilities left behind by Koizumi into assets by learning from his negative example and refraining from visiting the war-related Yasukuni Shrine.