IIRC, this manga has several one shots, all of them dark.
One chapter is about a couple with some age gap, they went to the countryside for good/vacation, they had steamy sex but the uke is having some psychological problems. He's so insecure of himself/paranoid that seme might leave him. Then, he began breaking things like glasses or phones. Then he somewhat went insane. At the end, iirc, the seme called the doctor to save him.

That's all I can remember. I hope someone remembers this manga. Please help me ;A;
Thanks in advance.

Mimurake no Musuko?

OMG Thank you!!!
I was actually thinking that the artwork is done by the same manga-ka and when I browsed vol. 1 in my files, I thought it's just about the childhood friend sexing with the brother of the main character. I didn't know there were one shots in it.

Again, thank you. You saved my life hehehe