That is not even what happens.
He has sex with the ML.
He is threatened into having sexual relations with another cop. So that's rape even if he organsmed. The reason is because he never wanted to have sex with the guy and hated doing it because it did feel like cheating on the ML to him.
When he was deeply depressed he slept with his friend, but that was more of a mutual comfort thing.
After that everything went to hell personally and professionally.
And it seems that in the years since that time he became the sex servant of his new boss. And it is not something he wants to do. He just gave up.
He gave up on everything he once cared about, even his ethics.
Honestly, it seemed as if he just didn't care what happened to himself anymore.
He wasn't having sex. He was being sexually exploited by his employer, in return for protection, again, a form of rape. It's not like he had a choice in the matter.
So no, he's not having sex with a bunch of people. He only had consensual sex with 2 people. The other times? It wasn't his choice.
Wasn't contradicting you, was actually supporting you, hit the last reply link.
OP needed context of the relationships going on because they thought it was a slutty uke sleeping around instead of a victim of sexual extortion by multiple people combined with spiritual suicide, he just gave up caring about life and went through the motions while waiting to find out what was going on with ML leaving him like that and what it all meant.
I didn't even read this Yaoi yet, but seeing the comments it seems it'll be a huge pain in my head and my kokoro. And since I don't like the sleeping around attitude for x reasons, I'm gonna pass on this one... Sorry Youka Nitta Sensei, most of your Mangas are great reads but I'm not gonna read all just because it's branded with your name.
Moral and virtues, self-respect... seem to be a thing of the past, thrown by the wiindows, whatever in fictions or reality. Sad...