Right now they're walking away from the edge of an enormous cliff. The boots and the tree are sitting right at the edge of the cliff, about to fall off the side of the flat world.
If you're not going for that scene, you need to correct the perspective issues.

I added a bunch of "buildings" or something, because the fact is, if you're not looking out at the ocean, you seldom see the true horizon line. It is obscured by hills or buildings or trees etc.
And since the viewer can see so far forward, if you have the path going straight back, you might have to put its origin there so it's not ridiculously long, or curve it until it's obstructed.
Now, I've not studied perspective or anything so I can't do it perfectly, but I'm just speaking from experience.