Your are using ISO-2022-JP-3. Hence you need to write your program as follows:
int main ()
{
// switch to JIS X 0201-1976 Kana set (1 byte per character)
printf ("\x1B(I");
printf ("\x33"); /* ウ */
// mandatory switch back to ASCII before end of line
printf ("\x1B(B");
printf ("\n");
return 0;
}
Note however that it is unlikely to be the character set expected by the terminal (on linux, this is most likely UTF-8). You can use iconv to perform the conversion:
$ ./main | iconv -f ISO-2022-JP-3
Alternatively you can use iconv(3) to perform the conversion inside your program.