US keyboard on laptop (QWERTY) Japanese IME input: before / after shortcut?

[レオンマ]

I'm on a windows 10 laptop, latest lightroom version. 

My keyboard is standard US qwerty but my input is Japanese IME. 

There's Roman letter input and Japanese symbol input options.

I also have UK English keyboard installed.

In none of these does the \ backslash shortcut for before / after work. 

I've tried pushing every key, it has disappeared. 

I just installed the US keyboard too and it doesn't work there either.

Shift + S doesn't work. 

Does anyone know this shortcut please. I know they can't be mapped, but I just need to know where it is hiding. 

Many thanks

[レオンマ]

Actually, it does work on US English keyboard. But to have had to install it, for one shortcut is very superfluous and frustrating. Could anyone tell me what the British English or Japanese input shortcut might be on a US keyboard? Many thanks