Ryu ga Gotoku - Language

I have just started playing the 5th instalment, and not long been learning Japanese, so while I dont really understand it i can identify and read most of the hiragana even if it make little sense to me at the moment.

However I noticed male characters using words like Iya as opposed to iie which I understand is another way of saying no, but I was of the impression it was mostly used by females.

Is this correct or am I misunderstanding, if it is correct is there a reason why male characters in the game use it? I forget what other words I have seen I thought followed similar pattern but sure I noticed others.

Can any body shed some light for me?

- "Iya" or "iiya" instead of "iie" is guy's speech. It has a bit masculine tone compared to "iie" to answer "No."

- The word "iya(na)" is an adjective (na-adjective, if you happen to know the classification) meaning "awful, unpleasant, something I don't like." Guys speech would be "Iya da" (I don't like it), and female speech would be "iya" or "iya yo" to say "I don't like/want it" as a curt refusal.

Thank for your reply, helps clear that up a bit .