Hi Shinhyo,
Again, I would ask to check that the folder you are having trouble saving to has any non-ASCII characters. For sure, ifeffit and demeter are not going to be able to handle folder or file names with non-ASCII characters.
Larch is slightly better at this - it can work with files with names in non-ASCII text encodings. To be clear, the situation with Larch is still not ideal, especially on Windows, because
a) the base installation folder can contain only ASCII characters, and cannot contain any spaces (apparently this is some problem
with other libraries or possibly some other variation on point b).
b) the concept of "localization" on Windows machines is sort of a mess and many libraries (at least, from Python) don't handle this very well. For Larch, we recently had to explicitly set locale to be "simple C / ASCII". That sort (or should!?) mean that you can read/write files and folders with non-ASCII characters, though I'm not certain that will work for all character encoding sets. It's possible this will get better with time, but it's not something that we can solve.
For ifeffit / demeter there is simply no hope for non-ASCII text to ever be handled.