If you have ever tried using a Japanese JIS layout keyboard on an English-set computer, you will soon realise that the unique keys that come with a split spacebar, right shift and backspace layout do not function without setting the computer to a Japanese locale. The keys still send scancodes however, so thankfully, you can make use of them with a little extra work.
Since the unique JIS layout keys always send scancodes, you could theoretically remap them with most software offering such functionality. However for ease of use, I am recommending AutoHotkey for USB or no-name actively-adapted PS/2 keyboards on Windows and Soarer's Converter for cross-platform use with PS/2 or older keyboards. For context, the two keyboards I will be working on is a IBM Preferred USB Keyboard SK-8806 (P/N 24P0459) with AutoHotkey and IBM Preferred Pro PS/2 Keyboard KB-0225 (P/N 32P5118) with Soarer's Converter.
Using a keyboard hook (AutoHotkey) or HID Listen (Soarer's), you should be able to find out what the scancodes of the unique keys quite easily. For the two test keyboards (and by extension, most compatible JIS keyboards), the maps below should be accurate to save you some time. Note that the grey keys denote keys that may or may not be present depending on whether you've got a Windows key model keyboard.
Now it's time to figure out what you're doing to do with the keys. You can either be really creative or purely functional with what you do. I opted to do something what I believe to be functional from my usually British ISO perspective.
I unified the split backspace area into two single unit backspaces, I added the \| key to the key gained from split right shift, added another backspace to the left of the small spacebar (emulating an Erase-Eaze configuration), extended the spacebar with the key immeidately right to it, and added a convenient delete key to the right of the new spacbar key. To achieve this functionality, you can use the code snippits below for AutoHotkey and Soarer's Converter respectively (and feel free to remove the code comments if you want).
To use the AutoHotkey code provided, you'll need to create an AutoHotkey script to put it in. Once AutoHotkey is installed, right-click an empty area of your Windows desktop, hover over "New", and then click "AutoHotkey Script" to create the file, then open the file in your favourite text editor and paste the code above in and save. Once done, simply double-click the script file to run the code. If you then wish to make this script run every time Windows starts up, simply compile the script via right-clicking the script file and clicking "Compile Script", and then follow steps 3 and 4 from these instructions from Microsoft on how to make an app run on startup.
To use the Soarer's Converter code provided, you'll need to create a
.sc to put it in. To do so, simply create an empty file with your favourite text editor, paste the code above in, and then save it with the
.sc extension at the end of the file's name. See my Soarer's 101 tutorial for instructions on downloading and using the needed flashing tools.
For a list of possible keys you can use for your own custom remaps, see AutoHotkey's List of Keys or visit the
codes.html page in the "docs" folder of the Soarer's Converter zip download (download location also described in my Soarer's 101 tutorial.