http://mysql.rjweb.org/doc.php/charcoll
SET NAMES according to the encoding being used by the _client_ (not the table).
Use the SELECT HEX() technique (in my link) to make sure the table is correct.
Which of these are you talking about?
mysql> SHOW COLLATION LIKE '%euc%';
+---------------------+---------+----+---------+----------+---------+
| Collation | Charset | Id | Default | Compiled | Sortlen |
+---------------------+---------+----+---------+----------+---------+
| euckr_korean_ci | euckr | 19 | Yes | Yes | 1 |
| euckr_bin | euckr | 85 | | Yes | 1 |
| eucjpms_japanese_ci | eucjpms | 97 | Yes | Yes | 1 |
| eucjpms_bin | eucjpms | 98 | | Yes | 1 |
+---------------------+---------+----+---------+----------+---------+
4 rows in set (0.00 sec)
mysql> SHOW COLLATION LIKE '%jis%';
+------------------+---------+----+---------+----------+---------+
| Collation | Charset | Id | Default | Compiled | Sortlen |
+------------------+---------+----+---------+----------+---------+
| ujis_japanese_ci | ujis | 12 | Yes | Yes | 1 |
| ujis_bin | ujis | 91 | | Yes | 1 |
| sjis_japanese_ci | sjis | 13 | Yes | Yes | 1 |
| sjis_bin | sjis | 88 | | Yes | 1 |
+------------------+---------+----+---------+----------+---------+
4 rows in set (0.00 sec)
I assume eucjpms and ujis, correct? I am not familiar with either encoding, but I suspect they are exactly 2 bytes per character? Or do they include 1-byte Romanji characters?
Use the SELECT LENGTH(), CHAR_LENGTH() technique to verify that the ration is 2 or slightly less. If it is about 4, you may have a "double encoding" problem, meaning that the table is corrupted.