I can only name them by their eyes

Uke = blue eyes = Ye Zi
Seme = green eyes = Gao Yang

I don’t think there is much to understand. The seme left, the father got beat, the uke moved in with another and decided to change himself. We then arrive at the present, where the uke is sick because he had his first time with the seme.

Oh thank you, I was just a liittle confused on what happened to the seme when he had hand marks on his neck and blood stains on his fist? Did I miss a chapter or something cause I didn't saw he faught the uke's father. And I really thought there's a flash back happened when they beat up uke's father cause after green eyed friends beat him, the seme doesn't have the hand prints and bloodbstains anymore.

*blue eyed friends

Oh. I too was confused about that part. But I think you are right about it being a flashback. The seme left the uke and then we are shown a flashback, where the seme went to look for the father while the uke was sleeping. I don't think you have missed a chapter. Perhaps we are not supposed to see the scene.

okay I'm starting to understand a bit, sorry if am kinda slow in this.

Corrwct me if I'm wrong, after the seme gave a hickey to the uke, I think that's where the flashback happened were he was banging on the door (probably the room of the uke's father?) then the magenta eyed guy was behind him as they planned to ganged up to beat the father.

The real question is how the hell did the green eyed guy got hand marks that probably he was choked and got blood stained in his hands? He wasn't even in the part were they ganged up the helpless father.

My speculation is that they faught before the magenta eyed guy came. In this pannel:

http://www.mangago.zone/read-manga/cry_for_me/uu/cry_for_me-chapter-33/21/

The magenta guy said "Do you think having a fight or two... will solve everything someone like that?" They probably faught first and probably he's been kicked out and start banging the door again. But, on that part, he doesn't have a bruised, hand marks on his neck or blood on his fist or something.

Ugh.... my brain hurts so much.

I like your speculation, but I don't think that is the case. The magenta eyed guy should at least have a scratch, if they fought. Besides, the seme had bruised from strangling and the magenta eyed guy doesn't seem violent enough to do that. My speculation is:

The seme gave a hickey to the uke and left to find the father. The magenta eyed guy followed him and ridiculed him for being weak and childish, since it was impossible for him to do anything by himself. The seme knew he was right, but he still went to look for the father. He found him and got beaten up, which is why he was the last one to arrive, when the uke woke up. Then he realised how powerless he was and decided to leave the uke.

Wait. I seemed to have misunderstood your question. I thought you meant that the seme and the magenta eyed guy fought.

Well, my speculation is still the same. I think the uke's friends took care of the father after the seme left. After all, it didn't seem like the seme was able to do it.