COY stands for Cross Over Yuri. The premise is pretty simple, I have a list I've compiled of over 500 cute girls from various anime and manga. I then use a random number generator to make pairing, which I then draw. Every third picture is a threesome.
If someone were to ask me to choose a pic in my history that marks the turn where I could divide the old pics from the new, it would be this one. I was so terribly disappointed with the last couple COYs, and some of my other work, too, that this one was a blessing to me at the time. Looking back, it's far from my best work. And yet, I still think it stands out. I was just starting to get the hang of real good, clean linework (not quite there yet, but this was a start), and it was the first pic where I really experimented with colored lighting. I'm also pretty fond of the pose, particularly Michelle (Michiru). Usually I have trouble with women in this position and, while this one isn't perfect, it's better than my other attempts at the time.
Also, as a side not, I absolutely love Sarah Adiemus, and intend to revisit her somewhere down the road.