This... this has to be a false positive by windows defender, right? 
Who knows man. When it comes to downloading games off of steam or other official apps, sometimes that pops up. I've downloaded an app before and my phone says its VERY dangerous but ive used it for 4 years. Up to you if you're going to download now or wait for the reply of the creator. :)
I've downloaded this game & have had zero issues or alerts from my other security software. I'd wager it is a false positive.
This is a false positive. The game is made on the Ren'Py engine, you can go to their forum where this topic is raised, and the developer describes this problem in detail.