Ptolemy, found some "bugs". At the beginning, when Alex introduce MC and Izzy she say "She is my sister from another mother", Izzy says nothing (i.e. agreeing with that). Later in the game Izzy clearly states that she and Alex are not related. Alex's words were supported by Agatha ("same blood" or something like that). But to Yuri's injury moment Alex and Izzy still behaves like they are not half-sisters.
Another thing, a small pharases exchange really. After Alex lost her virginity there's a choice for buying pill. Quite some time later in the hospital MC says that he needs to buy a thing for Izzy too. The same thing he did for Alex, explains MC in the next sentence. I don't get what they're talking about. I suppose MC is talking about pill he bought for Alex earlier. But in my game I chose to forgot about pill. And still see this text.