Japan's largest supermarket chain, Daiei , is embarking on seven months of leadership vacuum following an stock sales scandal involving its president and vice-president, a period which many analysts believe will prove disastrous for the company.An announcement made yesterday (10 October) revealed that Tadasu Toba and Kazuo Kawa, president and vice president respectively, had been demoted to directorships after reports of an insider trading scandal, which saw them pocketing ¥24m from sales of shares in