Disturbing images at the Nanjing Massacre memorial. Atrocities committed by Japanese forces here in World War II. Part of a history that continues to fuel animosity between the Asian powers. Anti-Japanese protests flare up in China regularly. And this year again, tensions are mounting over a group of small rocky islands in the East China Sea that China, Japan, and Taiwan all claim are theirs. Despite these outbursts, China has become Japan's biggest trading partner and Japanese brands are ubiquitous here. But could the fallout be bigger this time? Economics professor Yu Jinping (SOUNDBITE) (English) PROFESSOR OF ECONOMICS, NANJING UNIVERSITY, YU JINPING, SAYING: "The economic impact between the two countries will depend on the Chinese government counter measures. And I think the impact could be incredibly big. It could be a huge blow to economic relations between the two countries." (SOUNDBITE) (English) REUTERS REPORTER, JANE LANHEE LEE, SAYING: "Here in Nanjing, China's economic slowdown is already hurting retail sales and the dispute over the islands are creating an additional challenge to Japanese brands." This Toyota dealership in Nanjing told us 5% of its recent purchase contracts were cancelled by clients citing the dispute. In Shanghai, an annual marathon sponsored and named after a Japanese chemical company Toray is being rebranded. Consultant Hiroyoshi Ikeda. (SOUNDBITE) (English) CEO, MYTS, HIROYOSHI IKEDA, SAYING: "Right now it's difficult for Japanese companies to conduct large scale sales promotions. I don't think 2-3 months ago anybody expected this could have happened." It's been a tricky balancing act for Japanese companies seeking opportunity in the world's fastest growing major market. Advertising blunders such as Toyota's -- Chinese stone lions saluting the Prado SUV or a Land Cruiser pulling a Chinese truck have backfired badly. Japan's Mori Building had to change the design for Shanghai's tallest skyscraper after complaints a hole at the top resembled the rising sun on the Japanese flag. And as Beijing was considering which company's technology to adopt for its high-speed rail, online protests broke out against Japan's Shinkansen. But there's hope even with opportunities lost. In Nanjing shoppers haven't completely shunned Japanese brands. At least not yet. Liang Yan is a Nanjing native. (SOUNDBITE) (English) NANJING RESIDENT, LIANG YAN, SAYING: "I like digital products and the Japanese make them better. I've bought Japanese products even though in my heart I resist them. I only buy their digital products and nothing else." For now, most Chinese seem to be keeping patriotism out of their buying decisions. But any escalation of tensions will put 350 billion US dollars in annual trade at risk.