Affiliate Marketing Secrets

Understand Japan is second highest holder of US treasury bills of US , after China. Now if Japan’s own External debt is increasing. Its like a circle. Keen to know the non residents who have lent to BoJ / Japan. I did found some details on BOJ site, however that spreadsheet does not have details of lenders to Japan. I am simply trying to link back to countries holding US Treasury bills (part of US external debt). Japan is second highest holder. Though Japan itself has huge external debt. SO what are the parties which have lent to Japan. I am told on yahoo answers.com that this information can be secret. I feel this information should have been in public domain. but do not seem to find it through Google.