Well, I understood as much from that plot as from a Murikami Book.
What I liked:
The premise of demons and whatnot meddling with humans, the possibility of the character getting his powers from his own incest-created demon baby is intriguing. The idea of corrupting everybody around and sharing the harem with other guys is rarely explored, so - cool.
What I didn't like:
Starting In Medias Res is a cool approach, that can do a lot to make a story better. Sadly it's not the best execution of the approach. The player is confused up to frustration levels. In theory it should grab the attention of the player, promise him a bunch of interesting stuff and satisfy the urge of action, so that early-game grind is not hated. Here... I got nothing. I did not get exited for how we came here. I still have no idea, why would the character want to leave for the USA. And the dissonance between the synopsis and the game would probably win an award if anyone gives such awards. There are better ways to achieve reader confusion, without bringing in player frustration.
Navigation is a bitch. It wasn't that bad in the hospital, but at the players home it was horrid. Also - the door leading to the kitchen looks like a door to the street. Some form of pop-up information should be implemented at minimum. Dropping the whole "move around a map/house" would probably be better - it works great for sandbox games, but I have yet to see anything in this game, that promises a sandbox element.
The game is very plot-driven. Considering how less than 10% of adult games reach even a somewhat final stage, I consider this a negative.
Also the plot is confusing for the sake of confusing, not because of way too many characters and agendas mixing up. Aunt takes the award here: "Save my sister, only you can do it! But I Ain't telling you shit, except don't trust the devil!".
Is it just me, or does Selina look 30+ before the hospital?
As a whole I see promise, but it's way to early to be optimistic. Overall good work. But there is nothing making me want to replay the game. I felt railroaded in to a bunch of sex scenes with confusing drops of plot on the way. The characters are bland, lacking establishing moments in their introduction and desperately need more non-sexual screen time.