>>719801345
The SOUL doesn't do anything of its own volition, as far as we can tell. It's part of our interface to interact with the world of Deltarune and does things like glow or turn yellow when the story requires it to do so.
That's just a roundabout way of more or less agreeing that Deltarune is a video game and video games are inherently a constructed experience that always force the player to do things and can never allow for total freedom, but it's important to recognize that this is itself part of the game and its framing device established in the intro.