The 'scm_i_mirror_backslashes' in load.c operates on C strings in the locale encoding, and assumes that the locale encoding is ASCII compatible. In the Shift_JIS encoding, used in the "JP_jp.sjis" locale, backslash '\' is mapped to a multibyte character, and the Yen sign '¥' is represented using code 0x5C, the same code as backslash '\' in ASCII.
As a result, users of the "JP_jp.sjis" locale will have Yen signs '¥' in their file names converted into slashes by this function. Mark