Just Megumin's backstory, along with enhanced worldbuilding and foreshadowing of the main show. It really acts as a prequel and references A LOT (a lot) to events that will happen later, so if you liked Konosuba, expect to be *Leo pointing meme* at every other scene. Overall it's much more clever than humourous, whilst also being a very feel-good show with great worldbuilding. It's a definite watch if you're in for its clever hints and nods, as the show takes us to all three settings we've seen with the two seasons and subsequent movie. Oh and have I mentioned the lovely worldbuilding?