60-year-old Nishimaya's death came just three days after he mysteriously collapsed in Tokyo. While there are no suspicions of foul play, Japan has yet to announce a cause of death.
The timing of Nishimaya's death could not be worse. Nishimaya was due to head to Beijing in October to take over as Ambassador. The hope was that he could help diffuse tensions between the two nations over the islands known as the Senkaku in Japan and the Diayou in China.
The worry now is that it may take months to find a new ambassador, leaving the two countries in diplomatic limbo just as tensions worsen.