(Visual novels, for non-otaku, are like a choose-your-own-adventure, but with pictures and music.)
This one is part of the ever-popular "transfer student discovers their new school is weird" genre.
In this case, it turns out to be populated entirely by demons.
Fortunately, you aren't the usual faceless everyman VN protagonist. You're a serial killer.
The basic game has demon hunters, succubi, werewolves, and over 20 different endings.
You can play as male or female, each with their own unique storyline, and there are male and female optional romance sidequests for both characters.
There are also options to fund extended editions of the game. These take the basic edition and add new content:
Lovely
This is the version I would buy, if I were purchasing the game instead of writing it.
New romance options, more characters, and a whole new storyline focused on the relationship-building aspect of the game.
Deadly
I was actually thinking of @EndMaster when I made this version. XD Specifically, the several times he's complained about Bioware mucking up the story with pointless romance sidequests. So, this is for you: a version focused on grimdark.
More 'bad' endings, more options for NPC death, and a whole new storyline focused on the serial-killer aspect of the game.
Yes, the basic edition's romance is still in there, but you can ignore it. In fact, you can kill off all the love interests so you don't have to worry about accidentally triggering a love story.
Devilish
The Ultra-Deluxe version of the game. Has all the content from both Lovely and Deadly editions, as well as a third completely new storyline.