From Los Angeles Times (link):
A year after about 20,000 anti-Japan protesters jammed the streets here, Japanese and Chinese officials are still wrangling over how to repair a damaged Japanese Consulate building ” a reflection of the icy political relations that persist between the two nations.
But it is a different story on the economic front. Not only are Japanese restaurants that were attacked during the April 16 demonstrations back in business, but more than 525 additional companies from Japan set up shop in Shanghai in 2005. That’s about the same number as in the previous year, indicating that fears of a Japanese corporate pullback from China were unfounded.
See also Wikipedia’s “China-Japan relations“; also “Japan-China relations” by the Ministry of Foreign Affairs of Japan; and “Bilateral Relations with Japan” by the Foreign Ministry of China