To everyone saying "Why use Unreal Engine?", it's what the developer is familiar with. UE isn't specific to 3D games, just like Unity isn't specific to shitty Slender knockoffs, or Game Maker for Pac Man clones. If it works, the engine doesn't matter at all. Game seems to run fine, and the download size is fair. I'd rather have an engine with proper documentation and crash support than another unsupported Flash game or memory-leaking RenPy title.
Back on topic, man this game is skirting abandoned, much like the other games by this dev. For making several hundreds of dollars on their Patreon as well as having nearly two years of development, I'd like to see a lot more from them. Glad progress is being made, but it's frustrating to see and turns me off from giving any kind of money when many other developers do much more with less or no monetary incentive.