In suh is very selfish and manipulative! Threatening to kill him self!? Okay wtf and out baby had to give up music for him and he’s so stressed and in suh just adds more to the stress
In high school? when their relationship was taking a tumble and ML seemed like he was keeping his distance, In Suh said "I'll die without you," effectively chaining the ML to himself.
A couple of chapters ago, In Suh accepted an "invitation" from the play producer. It wasn't explicitly shown whether it was a sexual advance or not, but it was certainly implied and In Suh took his hand.
The "I might die without you" guilt trip reference (spans to the next page as well):
http://www.mangago.zone/read-manga/tractor_full_of_love/uu/ibx_chapter-10/pg-1/
As for the "cheating" I misread the page the first time, so he may not have cheated after all. I saw the reference to a "love shot" and didn't read the translator's note (that it was hooking arms like lover's to drink their shots), and assumed that they were going to go to a love hotel or something. But I am still weary of the scene, because the writer was obviously hitting on him. So it wouldn't surprise me if they did end up hooking up that night.
http://www.mangago.zone/read-manga/tractor_full_of_love/uu/ibx_chapter-15/pg-2/
I think the old man isn’t the one who beats the poor boy! And he can’t go against the duchess so I think that the old man actually really loves the boy but the Duchess gets jealous and beats him.
Doesn’t excuse that he lets it happen