STRINGS-CP932(1)
strings-cp932 - extract printable windows-31j/cp932 strings
strings-cp932 [-t format] [file...]
Strings-cp932 finds and prints strings containing printable Windows-31J-encoded characters in a file, default standard input. Printable characters are taken to be ASCII characters from blank through tilde (hexadecimal 20 through 7E), inclusive, and all other characters defined in the Windows-31J character set. If -t is passed, strings-cp932 prepends file offsets to found strings. The format argument passed to -t can be d for decimal offsets, x for hexadecimal offsets or o for octal offsets.
-n is not supported for now; even 1-character strings are printed. You can pipe the output of strings-cp932 to awk 'length($0)>n' (or awk 'length($0)-length($1)-1>n' if you're using -t) where n is the desired minimum length if you want to filter out shorter strings.
https://www.unicode.org/Public/MAPPINGS/VENDORS/MICSFT/WINDOWS/CP932.TXT - Windows-31J mapping table used by strings-cp932