This game is phenominal. I normally thing reviews which are early are really bad ideas. This one merits it. I could be a contrarian and maybe give this 4 stars and talk about some of the issues I do have, but honestly the art is phenominal. It might, no shit, be the best I've seen in any eroge I've played. Somehow blending pixel art and the depraved nature of the acts you commit basically flawlessly. The story just makes it hotter, which is basically the reason we are here and not at any myriad other porn websites on the internet. The only problems I have with the art is that it might be TOO good and later releases might disappoint. If only all of our issues could be so pressing.
As for the game part, it's...weird. It's clearly in development (which is why I hate early reviews but holy shit the art is just that good). But there are a few points of concern:
1) The dungeon sections are too vague, you can't tell what's happening. This normally isn't that big of a deal, it's even skippable. But I think the intent is to drive in just how much you're stealing from the hero (who is perfectly hateable). This won't be possible when you can't tell what's going on at all.
2) Vi. I actually really like her design (THE ART IN THIS GAME IS SO FUCKING GOOD) but she's a huge nothingburger right now. She needs to be an integral part of the plot sooner in the story, rather than later. She's your perky sidekick and it's implied there is some relationship between you two which is fine; but if you're going to try to tell a story where the protagonist might be swayed by Cecille's amazing body into betraying the demons, there should probably be a compelling demon you would be betraying, not just some member of royalty. Vi just doesn't do anything (early build, I know). It was super weird seeing this story being hinted at early on in the game.
3) The sex system just isn't that deep. It doesn't need to be, but there really could be some polish there. If the game is about you stealing, it'll be that much better when the player feels like his actions are skillful and now just "find the position on the right, hold the mouse button". There's some frustration system in place, but it just doesn't seem like it's better than just mindlessly doing the same thing and waiting for the beautiful animations to finish up.
But these are minor complaints. The game is an easy 5 with the art and the plot with the protagonist and the humans. The scary part is that this game is going to get better as it progresses.