Hello, all! Never in my wildest dreams did I imagine that these games would come to GOG, so I had 0-7 on Steam, and had beaten them already, but wanted to go back through in New Game + and sweep up some of the side content that I hadn't finished my first time through, as well as enjoy the story again. Problem is that the GOG version didn't pick up on my Steam saves automatically like they usually do, and they weren't anywhere obvious. Some of these were fairly easy to figure out with a little digital elbow grease, but this project took quite some time, and I figured that I'd post the information here so that nobody else had to figure this out again. I will throw in the disclaimer that PCs can be a fickle beast, and some of the information I'd seen about where to find save files was nowhere near where I found my own, but this worked for me, and hopefully, combined with the general tips I have, you'll be able to figure it all out for your own system. Big thanks to anyone who contributed anything anywhere so far; the old spirit of the Internet of people just helping each other out with obscure topics is still alive somewhere.

First, I have a few links that might have some helpful information:

+ https://www.pcgamingwiki.com/wiki - This has some information about where save files are stored for each game, but it's kinda spotty; I found it more useful for game ID numbers than anything else.

+ https://www.gogdb.org/ - Same as the above, but specific to GOG, I was able to find some game IDs here.

Now, some places to look in your own system for where these files might be. Keep in mind that I have two or three hard drives, with my C drive being more of a boot drive (it's tiny), and my V drive being where my main storage is, so games are installed here, as well as Steam itself (in a folder called Games), though Galaxy is installed on my C drive. Adjust as necessary for your own system:

+ V:\Games\Steam\userdata\[STEAM ID]\[GAME ID]\remote
+ C:\Users\[USERNAME]\AppData\Local\GOG.com\Galaxy\Applications\[GAME ID]\Storage\Shared\Files
+ C:\Users\[USERNAME]\AppData\Local\Sega (will have GOG after GOG versions)

General tips:

+ In the drive locatoins in the previous section, [USERNAME] is the username for you to log into your computer. If that's not something you do, and you're the only on who uses your computer, it's probably Administrator.

+ If you're new to PC gaming, and don't understand all this ID nonsense, you will have a numerical ID that identifies you on Steam. If you don't know what that is, it'll be a likely obvious folder in the Steam\userdata, and should be a long string of numbers.

+ Game ID is the same thing, and you can look up online (using the links above) what each game is, but Steam and GOG will very likely have different ID numbers for the same game. A neat little trick for the GOG versions, if you haven't played them yet, is to go into C:\Users\Administrator\AppData\Local\GOG.com\Galaxy\Applications\ and click on the Date Modified category at the top, to sort them in chronological order, then start the game up; since that's the first time you've played the game, it will create the folder on the spot, and since it's the newest folder, it'll float right to the top. That's what I did, and it saves a lot of time.

+ Make sure to transfer all necessary files! Yes the *.sav files are your actual saves, but you'll also want to transfer system.sys (system configuration, particularly options on the title screen menu) and *.clr (how the game stores clear data and recognizes files on which you've beaten the game), especially if you want to jump right into New Game + and/or Premium Adventure. Folders too, if it has 'em!

+ If you can't find your Steam save files for whatever reason, they might be backed up in cloud storage. Head to https://store.steampowered.com/account/remotestorage, and you'll be right there, and can download whatever you need.

Here's the tl;dr version, and probably what most of y'all came for: the game IDs, locations, and how to get it all working. Some will be easier than others:

Yakuza Zero
+ Steam ID - 638970
+ Steam Save Location - V:\Games\Steam\userdata\[STEAM ID]\638970\remote
+ GOG ID - 55966314534907843
+ GOG Save Location - C:\Users\[USERNAME]\AppData\Local\GOG.com\Galaxy\Applications\55966314534907843\Storage\Shared\Files
+ How to transfer - Just click and drag; nothing special here.

Yakuza Kiwami
+ Steam ID - 834530
+ Steam Save Location - V:\Games\Steam\userdata\[STEAM ID]\834530\remote
+ GOG ID - 56296604923139714
+ GOG Save Location - C:\Users\[USERNAME]\AppData\Local\GOG.com\Galaxy\Applications\56296604923139714\Storage\Shared\Files
+ How to transfer - Just click and drag; nothing special here.

Yakuza Kiwami 2
+ Steam ID - 927380
+ Steam Save Location - C:\Users\[USERNAME]\AppData\Roaming\Sega\YakuzaKiwami2\[STEAM ID]
+ GOG ID - 56296605295395873
+ GOG Save Location - C:\Users\[USERNAME]\AppData\Roaming\Sega\YakuzaKiwami2_GOG\
+ How to transfer - Just click and drag; nothing special here, but note the oddball location.

Yakuza 3 Remastered
+ Steam ID - 1088170
+ Steam Save Location - V:\Games\Steam\userdata\[STEAM ID]\1088170\remote
+ GOG ID - 56296605655234780
+ GOG Save Location - C:\Users\[USERNAME]\AppData\Local\GOG.com\Galaxy\Applications\56296605655234780\Storage\Shared\Files
+ How to transfer - Just click and drag; nothing special here.

Yakuza 4 Remastered
+ Steam ID - 1105500
+ Steam Save Location - V:\Games\Steam\userdata\[STEAM ID]\1105500\remote
+ GOG ID - 56296605971762165
+ GOG Save Location - C:\Users\[USERNAME]\AppData\Local\GOG.com\Galaxy\Applications\56296605971762165\Storage\Shared\Files
+ How to transfer - Just click and drag; nothing special here.

Yakuza 5 Remastered
+ Steam ID - 1105510
+ Steam Save Location - V:\Games\Steam\userdata\[STEAM ID]\1105510\remote
+ GOG ID - 56296606225266695
+ GOG Save Location - C:\Users\[USERNAME]\AppData\Local\GOG.com\Galaxy\Applications\56296606225266695\Storage\Shared\Files
+ How to transfer - You should be able to just click and drag the files, but the GOG version picked up my system and clear data just fine, my Steam saves just WOULD NOT show up. Someone else might have a better solution for this, but what worked for me was to make start a New Game + on the Steam version, save as soon as I could, and then transfer that New Game + save over, which my GOG version picked up and could load like normal. I'll have to start a regular New Game and watch the opening cutscenes and then load that to keep playing, but that won't be a problem the second time around.

Yakuza 6: The Song of Life
+ Steam ID - 1388590
+ Steam Save Location - V:\Games\Steam\userdata\[STEAM ID]\1388590\remote
+ GOG ID - 56296606511683989
+ GOG Save Location - C:\Users\[USERNAME]\AppData\Local\GOG.com\Galaxy\Applications\56296606511683989\Storage\Shared\Files
+ How to transfer - Just click and drag; nothing special here.

Yakuza: Like a Dragon
+ Steam ID - 1235140
+ Steam Save Location - C:\Users\[USERNAME]\AppData\Roaming\Sega\YakuzaLikeADragon\[STEAM ID]
+ GOG ID - 56296606783325117
+ GOG Save Location - C:\Users\[USERNAME]\AppData\Roaming\Sega\YakuzaLikeADragon_GOG\1
+ How to transfer - This one would've been a dead end, but special thanks to GOG user Garnet Sunset, who made this helpful tool: https://github.com/GarnetSunset/rgg_save_tools/releases What you want here is y7_cryptor.zip and y7_gog_cryptor.zip. Download them both, decompress/unzip them, and you'll have four programs total, two of which you won't be using. Click and drag your Steam saves into y7_decrypt.exe to remove the Steam encryption, and you'll get a new file with the same name, but the extension will be.json. Click and drag *.json into y7_gog_encrypt.exe to encrypt them for the GOG version, which will replace your original *.save file that's in that folder. If you're curious, the other two files are if you want to do this in reverse. Once they've been reencrypted, then just click and drag them into the GOG save folder. It sounds like a lot, but it's not super difficult to do.

Hope this was helpful; enjoy!