SOFTBANK GROUP CORP. 
By "Who is Jack Ma working for?" asked some on microblogs, hours after Alibaba Group Holding Ltd filed a prospectus for an initial public offering of its shares in the United States, which some say could be the biggest listing ever of a technology stock.
Ma was the lead founder of Alibaba in 1999 and has become something of a cult hero to entrepreneurs and many ordinary Chinese, saying he champions small business against industry giants.
"Jack Ma is a big traitor," wrote another user on Tencent Weibo, a major Twitter-like Chinese microblogging site.
In its IPO prospectus, Alibaba detailed ties with its two principal shareholders - Japanese telecoms firm SoftBank Corp, which owns a 34.4 percent stake, and Yahoo Inc with a 22.6 percent stake.
SoftBank invested in Alibaba 14 years ago, and Yahoo bought a 40 percent stake in 2005. Both holdings have long been public knowledge and have been covered in previous disclosures.
Yet this old information triggered a clamor of dismay and indignation among some anti-Japan Internet users in China on Wednesday, who also noted that Chinese native Ma is only Alibaba's third-biggest shareholder, with an 8.9 percent stake.
Some called for a boycott of Alibaba's popular trading websites - Taobao and Tmall - though that's likely to have little impact on businesses that brought in most of Alibaba's $6.5 billion of revenue in April-December.
TROUBLED TIES
The Asian neighbors - and the world's second- and third-largest economies - have a troubled history.
Japan invaded China in 1937 and ruled it with a brutal hand for eight years. Millions of Chinese were killed and tens of thousands of Chinese men were shipped off to work in Japanese mines and construction. Chinese women were forced to work as so-called comfort women. China last month impounded a ship owned by Japan's Mitsui O.S.K. Lines Ltd over a dispute dating back to the 1930s war. Mitsui later paid about $29 million for the release of the vessel.
In 2012, sales of Japanese-branded cars were badly hit in the fallout from another row between Beijing and Tokyo over disputed islands in the East China Sea.
"Calling someone 'traitor' has been (a custom) since the May Fourth period," said Zhang Ming, a professor of international relations at Beijing's Renmin University, referencing student demonstrations in 1919 against Japan receiving Chinese territory from Germany after the First World War.
"When it comes to why Chinese people make a big fuss, it relates to China's environment: China's officials don't stop this kind of behavior," said Zhang. "These past couple of years, there's been a massive clamor for populism and nationalism."
As one microblogger wrote of SoftBank's stake in Alibaba: "Oh my god, Japan's claws reach everywhere!"
(Reporting by Paul Carsten and Beijing Newsroom; Additional reporting by Sui-Lee Wee; Editing by Ian Geoghegan)
