Nissan’s chief executive, Hiroto Saikawa, is in the toughest fight of his corporate life. And it’s all Carlos Ghosn’s fault.

At least that’s what Mr. Saikawa has said for seven months since Mr. Ghosn — the architect of the Nissan-Renault-Mitsubishi alliance — was detained by Japanese prosecutors and accused of financial wrongdoing. Mr. Saikawa, once a loyal lieutenant to Mr. Ghosn, has relentlessly attacked his former mentor’s character and blamed him for myriad woes at Nissan, including failures of corporate governance and its sharp drop in 2018 profit.

But now Mr. Saikawa, a lifelong Nissan employee, is facing scrutiny — from shareholders, former colleagues, the press and others — about his own competence and probity.

On Tuesday, he presided over the company’s first annual meeting since Mr. Ghosn’s fall. Mr. Saikawa won reappointment to Nissan’s board, where he has served for 14 years, thanks to support from Renault, which controls over 43 percent of Nissan’s stock. Despite clashes that have soured the relationship between Mr. Saikawa and the French company, it chose not to challenge his leadership.