The yen symbol is \, it's just that for some reason Japanese fonts and encodings replace \ with yen.
In DOS in Japanese directories are seperated by Yen symbols rather than \ but its actually the same character - if you change fonts you should see \.
The ` mark is there somewhere, sorry cant remember the hard key combo, but you can get it using the onscreen keyboard - the Japanese layout has ` as Shift+@, as the Shift on the virtual keyboard is a toggle hit it and @ should change to `.
You could also use keyhelper to map this to a key combo to make it easier to type if you use it alot
Stu