1st episode felt like a drag, to be honest. There was too much monologuing, although some of it was technically a dialogue with a slime. It was used to provide exposition, which is fine, too... But I think this kind of exposition works better for books (and maybe manga in some cases). At least I can see this working when you have a first-person story and the character is thinking about the things, that introduce the world, its rules and characters to us. In a visual story, that anime is, it just feels monotonous. This episode could have been cut in half, at least.
Then there is this incarnation in the girl's head, which seems kind of pointless. It's a separate entity, that sometimes talks to her. I bet it will be used as a plot device to "rescue" the girl with the help of "otherworldly knowledge". Why, though? Her having a starless skill is already enough, especially since we all can probably guess, that it's not "starless", but it has so many stars, that whatever devices are used to measure it, can't see them.
I will give a chance with next episode, but I feel it will be more like a "cute girl doing cute things with her slime" kind of show, rather than something with actual story and character development. Especially since we kind of already witnessed her "development", which was a bit forced.