Windows Console is using UCS, and hence while Unicode 0~127 can represent ASCII(0x0 ~0x7F), 128~255 (and beyond) cannot.
Finally I understand why, the widely adopted UTF-8 is a variable-width encoding.
Extended ASCII 128 and above are used by UTF-8, either as continuation byte (128-191), or as indicator of the width of encoded bytes (0xCx, 0xEx, 0xFx).
It means that if extended ASCII is still in use, Unicode (or UCS) has no way to differentiate which is Unicode character and which is not.
After all, each byte has only 8-bit.