It's probably "Nii-chan"
http://www.mangago.me/read-manga/nii_chan_harada/
They aren't the greatest to read, but in real life people do stay and return to abusive relationships. I think maybe "Unfather" "Easy Target" and "Escape into Oblivion" maybe show the mental exhaustion and dependency of both characters at the end, meaning they both are essentially trapped in this misery. It is "nicer" though to read stories where both characters are able to have the insight and strength to just end a toxic relationship, I think maybe "Sabita Yoru Demo Koi Wa Sasayaku" is the only one that has shown this though.

Hey could someone help me find this mangas. It’s about this guy who is I guess trying to get the attention of this man who is like a child predator. The man use to mess with him when he was younger but when he got older the man no longer did which is when he started trying to get his attention. Sorry it was terribly explained lol.