In sacking his long-time mentor, Carlos Ghosn, as chairman of Nissan Motor Co., CEO Hiroto Saikawa has only bolstered his reputation for being a tough leader unafraid to antagonize people in the interests of business.

Thursday's board decision to oust Ghosn, one of the most celebrated leaders in the auto industry, comes after he was arrested in Japan this week, accused by Nissan of serious financial misconduct over many years.

Saikawa is described by company insiders as smart, exacting and results-oriented. He will have to marshal those qualities as he tackles reputational loss, legal and regulatory issues, as well as suspicions that the arrest was a coup engineered by board members unhappy with Ghosn and the alliance with Renault SA.