Yoon Jaehyuk is bisexual and he always knew it, just desperately tried (and still tries) to repress it.
I know the type. Just in the first chapter he started babbling about how much he hates The Gays as soon as he heard something about that, when no one pointed it out except something on TV. Those who talk ill about the LGBT+ community when no one asks them are very closeted themselves, almost always.
He's fooling no one when he tries to avoid Garam's dick, at worst he actually doesn't mind it, at best he likes the fact that Garam has the hots for him.
The next season starts in September, can't wait.