I kept thinking about whether Kang jun is in love with the empress without him realising it.
Same here. I think he hasn't realized his feelings yet or at least the depth of them and also he is the last sarvivor of his Kingdom's royal family so he has the responsibility to get back his nation and people. Also let's not forget how the other nations treated him, from the previous Princess using him as a pet to our female lead who took him in as a bed warming slave... Though she did change as the plot moved on but still It's not an ideal start lol I think his feelings are a mix of love, vengence/hate and guilt maybe?
Did the seme actually have feelings on the uke? I don't understand his thoughts. But again, you never know how psycho thinking.