I don't know how i feel about this potential route honestly. I don't mind incest ending, since it's implied that both the MC and FMC isn't real sibling, wich is could be that they doesn't related by blood or that she's his cousin or something, wich is permissible by law. The incest route is arguably the most common one so far in this type of story. That being said, a lot of people here seems to root for the friend, and honestly i couldn't for the time being. I know he's nice and all, but i generally doesn't like overly bubbly characters like that. Plus i always hate the tropes when they make the bubbly positive characters win over the more competent one, and usually the bubbly characters always come out as floppy, wich is quite cute when its a girl but as a man? I didn't see the appeal of that. Honestly if i want a FMC end up with someone, it would be the good and dependable type wich i couldn't see in both the friend who's overly bubbly it's kinda annoying to me, and the MC who seems to have some personal problem at the moments. All and all, by how the story so far, i could only see the friends as more of a comic relief so i couldn't root for him right now. If she would be end up with the friend, i hope the author make some development for the friend, make him more dependable or show us more of his good side, and then i think i could root for him. anyway, that's my opinion at least.
Ps: i also feel it's unfair that the MC got to do all the work only to have the FMC end up with the friend at the end, it just sucks. I know that the friend is the one who inspire the MC and a good guy and it's better than the other version yada yada..... I just felt that the friend is not significant enough as a character to get the FMC. As far as the story goes, i only see him as a comic relief devoid of any interesting characteristic, so if he going to be the end game, i hope egaki sensei do something about it. At least give him some character development or make him more prominent character. But as for now, i couldn't root for him.