Let me preface this with a big spoiler warning. I'm going to talk about a lot of stuff, and that stuff will assume you've already played deltarune. You'll be spoiled, and possibly
confused due to missing context.
I don't have nearly as much to say about chapter 1 as I do chapter 2. 1 is a lot shorter, so that makes sense.
The World
I'm afraid to say that the dark world this chapter? It's damn near flawless. I love the card kingdom so much. It's really unique, and all of the music is pretty much as good as it gets. There are a ton of side characters like Jevil, Shawm, and Rouxls Kaard that are all really interesting in their own right. It's great, I love it.
Susie (and Lancer)
Susie and Lancer's relationship is the beating heart of this chapter. It is a key component to what makes Deltarune work. You start the game hating Susie. She literally threatens to kill you. She probably didn't mean it, but she did DO it. She attacks enemies with wreckless abandon. Susie is not a likeable character at the start of the game. When she starts to befriend Lancer, that starts to change her fiery exterior cools off a little, and we see a part of her that's actually quite nice. This arc is masterfully woven, and if it works, it works. You leave the game wanting to be friends with Susie in the same way Undertale makes you want to be friends with it's characters. Lancer is likeable from the start. He's a weird little goblin boy who laughs like santa claus. What's not to love?
Ralsei
The lonely prince. Here's the question on everyone's mind; why does he look like Asriel? Why is his name an anagram for Asriel? Is he Kris' monster-sona? The frustrating thing about this is that all of Deltarune isn't out yet. We don't know these things. Ralsei definitely has some messed up meta knowledge. But without the rest of the game, I can't say anything else on the matter.