Any info on the disc build of the JP release? Is it natively a more stable and patched build, compared to the initial western release.?
The Japanese version has its own set of version numbers, v1.0 ships on disc, with v1.0.1 available as a day one patch. I have not tried it without 1.0.1 installed to see what state it's in. Out of the box with 1.0.1, it's consistent with the current patches for the Western release. Not sure specifically which patch, but footsteps are working. Megumi's Japanese voice is still clipping because it's too loud, so they didn't fix the Japanese voices for the Japanese version.
Japanese only, as previously stated, although oddly the buttons are Western style if you're running from a Western account. (X and O are the same as in the US release. If you're running from an actual Japanese account, O and X will be swapped to be consistent with PlayStation button standards in Japan where O is select and X is cancel) It clearly says "For Japan Only" on the back of the box, so don't expect them to patch language options in. Also "Yes" and "No" options on menu screens are English for some reason, instead of being はい and いいえ like they should be. So they at least forgot to force 1 thing into Japanese. (Edit: Actually, both of these things appear to be tied to the account language setting and not the region. My Japanese PSN account with language set to English still has Western style input and random menu prompts in English.)
Sadly, the Japanese version is recognized by the PS4 as the exact same game as the US / European versions. Thus you can't double-dip on trophies. When I inserted the game into my console for the first time, it didn't even have to do a disc install for Shenmue 1, which was odd. Despite them being recognized as the same game, the save files are not shared. I did need to do a disc install for Shenmue 2, plus the 1.0.1 patch.