Japan's death-of-a-hundred-million counterfactual and reconstruction

What would follow if Japan's proposed national-death plan were followed by the whole population?

The response anticipates worldwide shock and a reconstruction problem, with returning Japanese expatriates proposed as part of rebuilding the country.

The question imagines universal participation in Japan's proposed national-death plan. The response expects worldwide horror and trauma, followed by the problem of what to do with the islands and the Japanese state. One suggested path is to allow Japanese expatriates who wish to return to help rebuild the country under guidance. Comparisons with garrisons that destroyed themselves rather than surrender are offered as precedents on a much smaller scale. The scenario remains an extreme counterfactual, not a description of Japan's actual surrender.