Send a ticket, NA's GMs are really nice about things like that and there is no harm in trying. Though I don't see why they have to specifically state that you can get a female set on a male character and visa versa, usually they have to state it if its the opposite, since that means that players can miss out on a certain reward and there is probably less of a chance to get a good reward in cases like that.
If you can't do anything about it now, you should at least have the decency to let people exchange outfitters of the same category (summer, hunter, stadium) into the other gender if they wish to do so, since nowhere was it stated that you could get a female set on a male character and vice-versa. To add to that, consider not ever releasing an event with untradeable sets again if you value your playerbase and want to keep the game running for a while longer, it only makes your players and customers angrier and more frustrated at how you manage the game.
How to get this free coupon?Its not a free coupon, they are talking about the deal in here
I'm a new player.