Responses
You make interesting points, I didn't realize the fake brother had watched porn videos about that type of relationship. I was wondering, ok ok why does he think brothers do that?
I think what happens is like in the movie The Island, the hospital's ad says "no donors. No rejections" since the organs come from clones. That's why as one of the men said "the farm" "tell them beautiful words so their organs grow healthy and beautiful" etc etc
Since Kou's older brother died, then why not give them the whole living body? Not just the pancreas.
Ok if I grasped it out uhm correctly this fake brother was raised on that "good hospital" shown in the tv advertisment and is for organ transplant and since he looks so much like the original brother the people from the hospital (just a theory since the other guys called the man "doctor") they made him more identical to the original brother. You can see at the end panel that the fake brother watched something more likely Kou's ''brother scandal" shown in the early panels before the accident. So in my conclusion fake brother thought that's how brothers should act like all touchy and s*x which is honestly fcking sad