US billionaire Daniel Loeb, who last year failed in an attempt to spin off a key part of Sony, has sold his shares in the struggling firm, saying "more urgency will be necessary" to get it back on track.
Loeb's Third Point hedge fund in 2013 pushed for Sony to hive off up to 20 percent of its successful US-based entertainment division, which includes a Hollywood studio and music label, to make it more profitable.
However, Sony rejected the proposal, which had grabbed international headlines and was widely portrayed as a clash of corporate cultures, pitting a hard-charging foreign billionaire against one of the bedrocks of Japan's staid corporate sector.
While no details are available, Loeb -- who is known for his aggressive style in stoking change at target firms -- said last year that Third Point had amassed the largest stake in the firm.
Third Point said in a statement dated October 21 that despite profit warnings, a worse-than-expected electronics environment and slow macroeconomic reforms in Japan, it still generated nearly a 20 percent return on its investment.
"While, regrettably, the company rejected our partial spin‐out suggestion, they made some changes that were consistent with our goals," it said, pointing to cost-cutting and improved transparency.
It added that Sony chief Kazuo Hirai's team "deserves credit for transitioning away from personal computers this year and improving television profitability in 2015. They have also improved investor transparency".
However, it said Sony still has "a long way to go and we continue to believe that more urgency will be necessary to definitively turn around the company’s fortunes".
Sony shares slipped 0.62 percent to 1,897.0 yen in Tokyo on Thursday morning.
The once world-leading consumer electronics giant warned last month it would book a net loss of 230 billion yen ($2.14 billion) in the fiscal year to March -- more than four times its earlier forecast -- blaming a downturn in its mobile phone business.
The company also said it would cut the smartphone unit's global staff by 15 percent -- about 1,000 jobs -- and not pay dividends for the first time since its shares started trading in Tokyo in 1958.
Sony has cut expectations for sales in the money-losing smartphone business, which has been hit by weaker-than-expected results in emerging markets, as battles global rivals including Samsung and Apple.
A report this week said Sony has decided to exit the market for low-priced devices in China, as well as Central and South America.
Sony will lay off several hundred workers in China as sales of its low-priced phones in the country slow, Japan's top-selling Yomiuri newspaper reported, citing unnamed sources.