This game is looking promising so far and I look forward to trying out the first release. Honestly, I think the character models are well done and unique. I love MILFS, and the mom definitely appeals to me! The aunt is pretty hot, too, though if you changed anything about her, I would recommend the hair colour and/or adding some eyeliner. Anyway, good luck with this game! All you need is an idea that stands out a bit and some hot renders.
EDIT: Never mind about what I said about the aunt. I like her eyes in the later images. However, if she wants to put on makeup in future updates/scenes, I wouldn't be opposed.
By the way, I think you should do a stalking theme for the killer. Whatever his motive, there's a killer on the loose. Maybe give some details about a family he stalked and killed over a deliberate long time or something. This accomplishes three things that most VNs do not...
1) It creates a tense atmosphere for the audience. With the dramatic irony, we know that someone dangerous is out there, but the characters are initially aloof or feel unthreatened.
2) It develops a realistic dynamic for the characters. Everyone's aloof at first, but then dad disappears. Blood's been found outside. Whose? Footprints leading to the shed. A stranger in the backyard. All of this stuff ramps the tension. The police are stumped. Your family's scared, placed in an incredibly vulnerable position.
3) It establishes an intriguing mystery for the reader to solve. Who is the killer? Why has he targeted this family? Is it random? Maybe these questions won't be answered, leaving the killer's identity mysterious (e.g., like Billy in the original Black Christmas). This is one reason why I think Black Christmas is the best horror film ever crafted.
One last thing - I can help with the writing and/or the grammar if you'd like. I don't expect anything in return; I just think you could create something very original here.