Git quotes any non-ascii character by default, not only asian ones. There’s an option to disable this quoting behaviour.
You can disable it using the following command:
git config --global core.quotepath false
Or, alternatively, by adding the following snippet to your git config file ($HOME/.gitconfig usually)
[core]
quotepath = false
After this, git should show your filenames exactly as they are.
As to your other problem, git not adding a file with asian characters, I can only guess that it has to do with the encoding that git uses is not the same as the encoding your terminal uses. I hope someone else can jump in and explain that bit.