Euc-jp codec is a compatibility instance on these points:
 - U+FF3C FULLWIDTH REVERSE SOLIDUS is mapped to EUC-JP A1C0 (vice versa)
 - U+00A5 YEN SIGN is mapped to EUC-JP 0x5c. (one way)
 - U+203E OVERLINE is mapped to EUC-JP 0x7e. (one way)

If you need strict standard conformance, there's euc-jp-strict codec
for you.