Don't get the wrong idea. They're both male and women. Some of you might have heard of Book Section, a fancomic (which I haven't fix the fourth page and updated...) by me.
Aika, the one who was sitting far from the geisha was indeed a woman. The one with the lute is a male, Misaki Nue is the name, he was disguising as a geisha to assassinate one of the important man in the country. He's a great lute's player and a very skilled assassin.
The meaning of Misaki (another meaning that is) is the messenger of God; animal; fox/dog. Fox are cunning and they like to pull a prank on people so I thought taht would make a good name for him. As for Nue, the name means 'mysterious man'. So you can conclude that Misaki Nue is living a life full of deceit.
He attracted to Aika, because she was very honest and sweet and possessed some qualities that normal women doesn't have.
Hm, they're not really a couple, and Aika didn't know that Misaki was a man, not until the very end of the story.
Is this love in your eyes?

Oh, and happy birthday to liveverysecond~ *threw confetti* Sorry for the late B'day gift...:3

EDIT:

Here's Misaki's look before I turn him into a Geisha...Misaki Nue