Basically, you need a hook, that is to say a selling point that catches the notice of people. As its been said, the market right now is swamped with porn games of all kinds and just having a vague idea is like saying you have no idea at all.
You need your game to stand out. Let's just take a look at what you've said OP:
The MC is a demon? Yeah, and is such in a couple of dozen games.
There are transformation? Again, plenty of those games about.
Maps? Honestly that should be standard and not a unique selling point.
Sex mechanic? Well I'd certainly hope there would be in a porn game.
Look, don't take what we're saying too harshly. Most people want developers to succeed, but if you're trying to gauge an idea for a porn game at a time when porn games are everywhere, even on Steam, you need to have more than "Transforming Demon has sex" as your pitch. So, develop the idea more, get it to the point where you have a clearer idea and then start gauging interest. And for god's sake, that actually means having a basic plot, unique selling points of the game, a list of potential pairings, kinks/fetishes and tell people how the game will be played. Too often people have gone off, added a sentence and decided that was enough.