Whoo! Welcome to the "behind on buying consoles" club!
Is it weird that I didn't like Higurashi? It was the first time I saw the cute-dark style, and I hated it so much, it felt so overly edgy. Nowadays I'm used to the style, but I haven't watched it since the initial viewing. I should check it out again, maybe I'll like it more. Well, I already suggested the cute ones, so here are the not cute ones. Lol
Some of these aren't super dark, but fall under psychological imo, also some of these don't start out calm but I figured I'd throw them out there anyway.
^^^This one is discontinued, and more wholesome than dark, but it delves into mental illness and such.
^^^This one is more strange and surreal than dark, but it's definitely psychological.
I also have Drop-Out and Fresh Meat, but I've suggested those all over the forum already (And recently.) so you probably saw them.
I'm not going to properly promote it, but I'm also working on a dark, psychological, slowburn hurt/comfort type of drama. The main focus is domestic abuse, mental health struggles, childhood trauma, bigotry, eating disorders and eventually self-care. It is intentionally an uncomfortable read though, the MCs can be super flawed and problematic, it's meant for a 17 or older audience and the art style is also not too pretty. All the characters have a little bit of an ugliness to them. For you it may also be a bit difficult to read since there's slang and intentionally bad English grammar. If you're the correct age and interested in something like that I'll link it, otherwise I'll just leave it off at this.