
So the one who actually was dating the chairman was the younger brother, correct?

So in order for it to seem believable that he was at the crime scene instead of his brother, he would've had to leave some kind of DNA behind. Since the crime scene is full of bodily fluids, he needed to make sure that his fluids were there in order for it to look like he had just finished having sex. He didn't actually sleep with the chairman, he just masturbated near/on him so that if they tested him, it would match the storyline of what had happened.
I hope this explanation helps
I just finished watching season 2 of Partners For Justice, and I was thinking what if it was Yaoi instead ⁄(⁄ ⁄·⁄ω⁄·⁄ ⁄)⁄
Is that series good? I have it on my list but I haven’t gotten around to watching it