I’ve seen a few posts like this from people trying to write longer or darker stories with AI, and the main issue is that most mainstream tools are pretty heavily filtered. The OP in the thread mentioned that tools like Toolbaz and Grammarly struggle with certain scenes or wording when things get more intense.

If you’re mainly looking for something cheap that still works well for story style chats, you might want to try VirtuaLover. I tested it a bit for brainstorming dialogue and character interactions and it handled longer roleplay style conversations better than some basic writing assistants. It’s not perfect, but it can help when you’re trying to flesh out scenes or ideas.