I like me some dimension-hopping plot, and this one was very sweet.
For the implementation of the theme it is very minimal, and not affecting much or influencing the story nor does the message of the tale actually do something for the two.
The story was cute, short, and sweet, though there are a LOT of question about "Why does he keep dimension hopping?" Doesn't matter much other than it's a plot relevant thing that, unfortunately, a solution wasn't found. "Damn he just has hypnosis ok." And it is at least an easy way to have a guarantee for the guy to be safe in any world. Unless he is back home, where the mental effects of the fungi (very Last of Us) probably won't be affected by it, I would ask why that happened, but I brush it off as "AU things" though his mother died so it was a very "Oh." Without much deep introspection on it, but I guess it's also fine. I think all is just fine, sweet, cute, and does what it needs. I really like at least that concept of "In every universe, I still love you."
The writing, I don't think had any issues with grammar or tone, but nothing awe-inspiring as well.
The presentation is very nice though, I love the variety in sprites for each El and how each of their clothing represents the world they live in. And the backgrounds, I like how it all looks, very geometric but they serve their purpose well. Also the look of the Fungi creature looked neat.
A 2, 4, 4, 4, 4 for me.