Newfound enthusiasm for Sony Corp., seen in a surging share price, owes much to Chief Executive Officer Kazuo Hirai¡¯s November 2013 decision to elevate someone from the Internet services unit to push through painful changes.

Four months later, Kenichiro Yoshida went from relative obscurity to become the CEO¡¯s right-hand man and chief financial officer. The 55-year-old has used the mandate to cut jobs, sell off Sony¡¯s iconic Vaio personal computer business, spin out its television set unit and rein in the company¡¯s destructive market share ambitions in smartphones.

¡°He started the most important thing that Japanese companies cannot do ¡ª exit,¡± said Atul Goyal, a Singapore-based analyst at Jefferies Group LLC whose ¡°buy¡± rating has delivered an 85 percent return to investors in the past year. ¡°If you remove Yoshida, this stock is no longer a ¡®buy.¡¯ It¡¯s probably a ¡®sell.¡¯ ¡±