Here I go.
Main protagonist who has inadvertently trapped their "soulmate" John in a desolated wasteland of their own creation is desperately seeking them out to make sure that they are still alive.
That is, the main protagonist is a writer who has run out of ideas for potential stories, and has somehow willed the deserted area in the thumbnail into existence. However, the one creation which they still have passion for, the character named John, has been trapped in this place as a consequence. Without any way to enter this quasi-imaginary landscape, the protagonist can only write messages to John on their typewriter, hoping that they are somehow "transferred" into John's reality, enabling him to see them. The protagonist's goal is to make sure that the last spark upholding their creativity isn't extinguished forever.
That's my take on it! (Keep in mind, I haven't read your series, so I have no idea what I'm talking about in the slightest).