MS Mincho and MS Gothic (and many others including Meiryo) both use the Yen Sign (unicode 0xA5) character graphic for the Backslash character. There are also a

MS Mincho and MS Gothic (and many others including Meiryo) both use the Yen Sign (unicode 0xA5) character graphic for the Backslash character. There are also a few Japanese fonts (such as Sazanami Gothic) that don't do this. The separate halfwidth yen sign does not exist in Shift-JIS at all. So any time a non-unicode Japanese Win32 application needs to draw a halfwidth yen sign, it must draw a backslash. And you can't make the official character mapping convert Backslash 0x5C into Yen sign 0xA5, otherwise all file paths would break.