It seemed like an extraordinary display of patriotism and unity: Japan¡¯s biggest companies would come together to save their own, whether ailing carmaker Nissan or besieged convenience store giant Seven & I Holdings.

Roughly six months later, ambitious plans to merge Nissan with Honda and take the operator of 7-Eleven convenience stores private have both fallen apart, leaving them grasping for solutions and potentially even more vulnerable to foreign takeovers.

The failure to find a fix that would keep two of the country¡¯s most famous brands under Japanese control marks an unprecedented opening in its corporate landscape, and shows how hastily conceived rescue plans can succumb to market forces.