Shift-jis codec is mapping 0x20-0x7e area to U+20-U+7E directly
instead of using JIS X 0201 for compatibility. The differences
are:
 - U+005C REVERSE SOLIDUS is mapped to SHIFT-JIS 0x5c.
 - U+007E TILDE is mapped to SHIFT-JIS 0x7e.
 - U+FF3C FULL-WIDTH REVERSE SOLIDUS is mapped to SHIFT-JIS 815f.

If you need strict standard conformance, shift-jis-strict codec
is your friend.