Yeah, that's the most common ending in NTR. But if I remember correctly, the last update ended kind of open, indicating that they want to try to lift the curse and move away.
I mean, if it was some boyfriend or husband, it's one thing, but abandoning her little brother feels kinda off. Also, the whole game was initially not too serious, so it just doesn't feel right if it ends so badly. Maybe it will be something in the middle, like him accepting her corruption or something like this
Tbh, as I played the game years ago it was just an corruption game with maybe mild NTR in mind, but not really as the MCs did show anyway affaction toward each other. Since I replayed it, it's like an different game. )