Japanese carmaker Nissan has been dealt a huge blow as CEO Hiroto Saikawa has resigned. The brand is still struggling to recover from the ousting of Carlos Ghosn last November. Saikawa's departure was announced by the company's board of directors which is effective from September 16. Chief operating officer Yasuhiro Yamauchi is now acting CEO of Nissan till a successor is found. Saikawa admitted to being overpaid.