Spoiler (I think)
I think that the younger brother force his older bro again. The older wants to stop but his brother breaks down, cry and beg him. The older bro lets him do whatever him want.
He feels smt to his senpai. They hang out and eventually kiss.
Finally, the older bro tells senpai the truth about his relationship with the younger bro.
I rememberd the first page of the story. 7 year after the beginning the manga, both of the brother look like adults, wearing black suits. and we have the inner thought of the younger bro.
I thinks that scene tells us they don't end up together, at least not at the moment.
Wow forgot about that opening scene, I'm scared now. I looked at the raws and thought to myself "there's no way they will end up together.The relationship is too toxic for the older brother and he genuinely seems to hate younger brother now". But that opening scene (which as you point out, looks to be some time in the future when both of them are adults) leads me to believe that younger brother STILL yearns for older brother and hasn't gotten over him. Younger brother is so persistent that he's sure to continue causing problems for older brother even if they aren't together. I really hope sempai comes around and helps older brother (looks like they broke up as of the end of volume 2). Older brother really didn't want to tell him what was going on and his fears of how sempai would react came true. No wonder rape victims keep quiet... ( ╥﹏╥ )
If my reading raws correct, sempai shocks of the truth, and at the end of chapter 9 or 10, he cried or has watering-eyes. I think he would not deny older bro, hope so
Does anyone understand the Raws? If so can someone please explain it to me I'm so confused ..