If you are a Japanese national or have the right of permanent residence in Japan, you may apply for JSPS Postdoctoral Fellowships for Young Scientists http://www.jsps.go.jp/j-pd/index.html. We can help your application.
If you are a foreign researcher, you may consider JSPS Postdoctoral Fellowships for Foreign Researchers http://www.jsps.go.jp/english/e-fellow.
If you are interested in one of the above programmes in the research area of general relativity, cosmology and gravitation, please contact harada*AT*rikkyo.ac.jp.