I knew I had seen it around, so I had to do a little digging to find it again. So, Japanese Subaru dealers likely have their own service, which I have not yet found.. it is probably on some sort of Intranet that I would not have access to.

That said, there is a service called FAINES by JASPA (Japan Automotive Service Promotion Association). It allows independent service companies access to service manuals for all of the domestic manufacturers. The problem is that you must be registered as a repair facility with JASPA to use it. There is a "free demo" where you can get in and look around, but the only Subaru service manual available with that login right now is for a C-type GT7 Impreza (2019 model year).

You can find that service here: https://faines.jaspa.or.jp/enduser/user/login. There is a page with the login information for the "guest" user if you want to check out the GT7 manual.