The presentation is kind of rough, first of all – the UI is both really plain-looking by itself and not that different from the Ren'py defaults, even using the same font. Besides that, there are a lot of "missing image" errors. The backgrounds feel well-chosen, however, and the dungeon in particular is a nice interpretation of what that could look like in an urban fantasy setting. I also like all the things the game does with sprites, even if animations aren't as plentiful as they could have been.
In terms of writing, The Greener Side is not a bad read; the pacing feels fast even with all the travelogue in the beginning, the character voices are distinct, and the tastefully implemented worldbuilding wisely prioritizes fun details. The frequent punctuation errors (most often a missing comma) are kind of distracting, though, and some character backstories are exposited smoother than others.
I think the story's greatest strength is feeling appropriately tropey, with the isekai conceit and various other fantasy elements being given an entertaining, gently satiric spin. The ending feels way too brief, however – I'm actually not even sure if this was supposed to be it or if there's more to come, which I guess various unresolved plot points suggest. (It's also very sudden in its implementation, with the instant kick back to the title screen feeling slightly jarring.)
The overall lack of polish betrays that we're dealing with a game jam project, but the story is inoffensively realized and eminently readable. I honestly had a pretty good time with The Greener Side, just wish things could have been pushed a little further all around.