Japanese voiced and unvoiced characters

[Ken Guiche]

MySQL doesn't seem to differentiate Japanese Dakuon (voiced) characters and Seion (unvoiced) characters. For instance SELECT query won't differentiate "きず (kizu = wound in English)" and "きす" (kisu = kiss in English), so when I run a query like "SELECT * FROM mytable WHERE mytable.pronunciation = 'きず', it returns the entries with both "きず = kizu" and "きす = kisu".
I've tried changing the character sets and collation of the table to all the combinations I can find, but it hasn't made any difference.

Am I doing something wrong, or is this the normal behavior of MySQL?

Thank you,