I made an account just to give my useless thoughts.
I checked this out after seeing a clip on Youtube, people said to stay away from the manga, but there have been plenty of weird incest stories that work out fine, especially when they're not blood related. But this one just feels bad, I'll come out and say I'd have no real problem if the story started with Rin at 16+ and falling for Daikichi, if they're both eventually consenting adults then I ultimately don't care, especially since Dai has been written to be quite considerate and caring of Rin's feelings.
But the majority of the manga is with Rin being an adorable child, she's innocent, and while there's a time skip it really just feels like you watch her grow up from a cute little girl to a beautiful young lady, you get put into Dai's POV so I was really surprised how the whole "Rin LOVES him" came about. Kouki being such a creep was really bad as well, I get that he's a dumb teen who's in love with her, but he's so forceful about things with a girl who's made it clear she doesn't see him that way, and to top it off HE is the one to spill the beans.
The worst part of all is the literal ending sucks, they're having dinner and we don't even see a reunion, as if a few years at college is a long time anyway, I'd have preferred for everyone to have had a happy ending, Kouki meets a girl and is engaged when he comes back, Rin is expecting and is more grown up so it feels a bit better with her being a more mature woman with a guy twice her age, but it ends so abruptly.
Overall it was a nice story, at least until Rin's feelings came to light, I think most of us would have preferred Dai and Kouki's mother to have gotten together since that actually makes sense. Like I said, weird incest is honestly fine to me if it's done well, at the end of the day it's two consenting people who are fully aware of the potential problems and difficulties it would bring, if siblings and such didn't have a higher chance of birth defects, our societies would be MUCH different if all the inbreeding royals didn't naturally die so early from all the chronic health issues. The story is split between two themes that don't work together, one is a feel good slice of life that warms your heart seeing Rin grow up, the other is a romance against the odds, maybe if Dai was in his early 20's I'd feel better, but yeesh, a guy approaching his 50's being intimate with the girl he raised? It's just wrong.