Sometimes, you just want a face full of oldschool nukige clichées.
And when you do, a game like this is here for you.
However... I'm still giving this a 2 out of 5.
The art and music would have been a 4. But the writing is just sub-par. Not bad per se, but IMHO it's just boring. At least for me, the whole thing was a slog.
There's zero buildup. Literally the first scene you see is the MC and his sister in bath with eachother, and it's blatantly obvious right off the bat that she wants him badly. There's a blink-and-you'll-miss-it moment where the MC admits that he feels the same way about his sister, but it takes place during... an internal monologue. The whole thing has zero emotional impact.
But the worst thing is - this is just not a very good yandere story.
This is not a tense story where you can practically taste the victim's fear. This is no story that will leave you anxiously wondering about what's going to happen next.
Hell, you don't even get to make any choices. It's a kinetic novel, so it's really nothing but a slideshow. That also takes out a lot of the suspense that it might have had.
The MC is a faceless nobody with no personality and no motivations. He barely even shows emotions. Whenever his sister pulls crazy shit, he's just like "Oh hey, this is not normal. I should probably talk to her about this.". Anything he says or does falls flat. Not that his sister even listens to anything he says...
(seriously - take out every single one of his lines and >95% of her dialogue still works)
The dynamic between the MC and his sister is just everything that you do not want in a yandere story. It's bland. It's boring. And it's oh so fucking predictable. It really is just run-off-the-mill porn dressed up as a yandere story.
So, again, it's just a very typical nukige.
If porn is what you're looking for, then go for it.
But if you're looking for a proper yandere story (and odds are that you are if you're reading this), then... you're better off looking for something else.