xuran what OS?
and are you looking at the VS console or the godot debug? It's probably the VS console. (see if the problem happens in godot)
which would make this a VS problem, not a godot problem. something is configured wrong or it's not detecting the special characters, or just a problem with VS only accepting normal ASCII.
it IS printing FOUR characters which means it's reading half-and-half of a full character. so it's sending the data into the console, but the console is unable to make sense of this because the characters have TWICE the size (in data) of a normal character (that's how extra characters work). so you need a console/terminal capable of understanding it.