Well, as to if it's incest. I'd say it's not technically incest, but it's certainly crossing into some sort of grey area. That's why I think some people like the sort of taboo concept it and shows like it that have tackled the step sibling relationship angle. Now my opinion on the ending however, I don't know something about it felt kinda rushed. I heard manga readers saying there was a lot cut and not fleshed out to fit into 12 episodes, however I am only going on what I've heard, though I can totally see that being the case with how things wrap up so quickly.
I especially didn't like Rui's treatment by the end. I don't like her going back after him after everything that happened. She always ended getting the short end of the stick sometimes and I felt it wasn't like her just to jump all over him, even if he was starting to get better as a person and chasing his dream of being a author. I don't know a lot of it felt really hollow as far as an ending that gave that much closure. Don't get me wrong, I enjoyed it for what it was. I kinda think of Domestic Girlfriend, as least when I watched episode week by week, as my weekly soap opera. It's cheesy and not gonna be that much in terms of story, but so much happens and it filled that role until the ending, and I think that is where the anime kind of fails. I'm glad you enjoyed it more than me man though.
