NHK has just completed releasing what is possibly the only complete, Japanese-friendly Ring Cycle on Blu-ray. The recordings are conducted by Daniel Barenboim and directed by Guy Cassiers, from the Teatro alla Scala in Milan Italy, between 2010 and 2013.
All of the operas were released by Arthaus Musik in other major territories (Asia, Europe and North America), but NHK must have licensed them for Japan and, as such, have produced their own Blu-ray editions. Note that unlike most opera BDs sold in Japan, these are not imports or international editions with Japanese subtitles, but true domestic Japanese product.
After
Das Rheingold, NHK has granted the longer three operas two-disc sets. All of the operas should contain 48/24 LPCM 5.1 and LPCM 2.0 audio, and Dolby Digital 5.1 audio tracks.
Clearly, only Japanese subtitles will be provided.
I think I shall get
Die Walküre at some point to compare it to my Arthaus Musik copy.