I definitely agree with you in that Hongrim's character is meant to highlight how he has been sexually enslaved by the King, instead of being biologically gay; compared to the King's clear and sure sexual orientation. However, as a viewer I definitely felt that they were one and the same. Either way, I cannot imagine a more controversial topic but then again, it's Yoo-ha. Still, to say that my jaw did not drop at all those explicit sex scenes would be a lie.
I felt that all three actors played their characters beautifully. The Queen was icy and hateful in the beginning before she began to thaw. Hongrim was undoubtedly and fiercely loyal to the King, not to mention madly in love whilst in the eyes of King, there was no other besides Hongrim.
No one can even remotely argue that Joo Jinmo has never and will never be viewed as another pretty face. In fact, this movie has confirmed him being catapulted into the likes of Jung Woosung and Lee Byunghun.
But if I were to pick my favorite, it will still have to be Jo Inseong. While Joo and Song delivered their roles crisply, I felt that I was always wondering about how Hongrim truly felt and therein lies ALL the emotions and mysteries of this movie.
Though I did say that Yooha's piece can be viewed as comparative literature between cultured and innate sexual orientation, I'd like to think that it's actually about how TRUE LOVE knows NO gender and that in this love story of our three doomed protagonists, there just cannot be ahappy ending.