It's a visual novel with multiple routes adapted into an anime that's split into arcs, one arc per girl. Then it goes through a lot of different girls and the different routes.
It's incredibly NSFW though.

It's a decent watch i was just mostly kidding because of "Didn't think i was going down the incest path!!" and one of the routes is his sister.

Yup. It's twincest.

“Bah, although brother and sister can’t marry each other.”
“Don’t pull me back to reality every time.”
At least in the day I successfully confessed, allow me to enjoy this dream --- really, what a cruel imouto-sama.
“I have told you many times before, don’t mix up reality and games.”
“You are right.”
We live in reality --- not in games.
Even after our confession, after our hearts connected.
In the end, we will have to return to reality.
“On those little sister-based eroge that I gave you, most of the time both of them have a happy end without the story afterward.”
Two of them live happily together forever. Congratulations, congratulations.
But just a small imagination could tell that waiting for them is not only happiness. But saying it out is too harsh, so let the story end here.
There are also endings that have very grim conflicts with reality, some with determination to break all obstacles, some with elopement and the like --- the kind of endings where the battle of the anikis have just begun.
We will definitely show you that we are going to live happily --- just watch
We couldn’t have any references. The only reference that we could find only contained the confession part.
“Although you didn’t play it, but many little sister-based eroge don’t have that kind of ending.”
Kirino spoke in a tone as if it’s nothing.
"There are also those masterpieces with fierce struggles and tear jerkers."
“Um.”
Is that so? There are eroges that show a sibling’s love that faced harsh reality?
However, none of them appeared on the little sister-based eroge that I played.
None of them were included in the eroge that my little sister gave me.
Why? Do you understand why?
I understood.
Apparently it is a good narrating principle for the narrator to be somewhat crazier than the reader. I think I had gone overboard a few times. Sorry, I will not do that again.
Now, I’m not the ‘me’ from before.
Not Super Kyousuke.
So I decided.
“Thinking about it, those little sister-based stories are indeed pretty difficult to finish."
“What are you talking about now? It’s not limited to little sister based eroge. It’s the fate of all little sister based stories. In manga and alike, the female protagonist is a little sister. No matter how good the author is, in the end they still have to face the ‘blood-related sibling’ obstacle, so after reaching the conclusion they don’t know how to finish things up.”
Blah blah blah ---- as soon as my imouto started talking about ‘little sisters’, she could keep ranting for a while.
Innocent and naïve --- yet very carefree and happy.
That is my little sister, who I unconsciously fell in love with.
“However, in the end, because they are brother and sister, marriage is extremely difficult. So there is a development that after they confess and marry, they find out that ‘they aren’t actually blood related’.”
The biggest problem disappeared. Congratulations, congratulations.
“This rarely happens in eroge. Because the player will get angry.”
“Angry?”
“Very angry. Sometimes an idiot will even break the disk.”
Otakus are so scary!
“Two years ago, I saw an anime on TV that had the exact development that you just said. Bah, although the main story wasn't about ‘sibling' love, so it was okay. But recently the industry has been rejecting those ‘stepsister ending’ tendencies. If they are not blood related, it should be made clear from the beginning that they are not blood related."
“I’m slowly failing to understand what you are saying.”
Your nature is coming back.
“In the end, in a little sister based story, if it’s the real imouto then writing the ending would be very hard.”
“Really. Aren’t you reaching the same conclusion?”
“So I say, did you hope for this kind of development?”
“I’m telling you, you are the one who shouldn’t mix reality and games together!”
Although our appearances really didn’t look alike.
But I honestly never wanted us to not have a blood related relationship!
If I told my story like that, then that means I lost my right as a narrator.
It’s the same level of a lying narrator.
“Imagination is imagination. A dream is a dream. A game is a game….in reality, we are blood related brother and sister. We can’t marry.”
“If we don’t decide --- what to do.”