Actually, he wasn't attracted to kiichi. Angelo likes the older brother, yujin, and he uses kiichi to get to him since the butler do not allow him.
Kiichi is an actor and a famous one, and Angelo is a director, even if he doesn't like him but it's the job who's calling....
Kiichi is a selfish bastard he doesn't want to share. He wants shingo for him and only him. If it wasnt for shingo's affection and masayans brotherly love for shingo he would have kill masayan as well. But he respected him just for shingo.
I don't buy that. Why kiss him? Why ask him to sleep with him? Angelo is clearly attracted to him too. No need to sleep with him to get to the brother. Just offer him a job and then try to get the brother to show up.
Shingo has offered sex to his guy friend a couple of times. When he gets into a fight with Kagami. If the guy wasnt straight, would he have gone through with it?
Kagami went from caring about Shingos feelings to doing things to feed his insecurity. Spending nights out with the guy who kissed him. I get that he is not attracted to the guy. But why is it necessary for him to spend so much time with him? He is clearly rich. Why willingly follow a guy that is attracted to him, and leave Shingo behind?
There was no resolution to their problems, so the manga ends in an empty way.