You can do that in Unity by fading out an image. To better explain it: this is a 2D game but editor is 3 dimensional, which means that you have buttons, images, texts stacked on each other in correct ordear so they are overlaping as they are supposed to.Is there anything you can do like add motion blur or what technique some others use here between each frame to make the "animations" look smoother? I don't know much about Renpy but some games that I can't think of off the top of my head look pretty good and I think there's some blur in-between each frame
So to make this fake animation you have to have one image on top, and second already waiting beneth it. All you need to do is just to fade out the first one. This can give really decently looking illusion especially if only a part of body moves and you keep the rest in the exacly same spot as in the previous image(this makes it look like just the moving part is fading out and being blured)