Thank you for playing EDDA Cafe! As for game engine, we used Ren'py for all of our games so far. It also has a dedicated forum that still active to this day called Lemmasoft (https://lemmasoft.renai.us/forums/index.php). I've seen people make RPG-ish game using Ren'py but if you plan on having a lot of gameplay variations, I think Unity will be better for you.