There are already several models "in the wild" designed specifically to produce anime-styled "adult material". In Stable Diffusion for image generation, NSFW filtering is basically a post-processing step that can be disabled in a single line of code. I'm sure someone has already done it for Chat* models as well.

I would note that

1. ChatGPT is just OpenAI's default model with a specific prompt and interaction-buffer rewrite model; and

2. you can sign up, for free, for access to OpenAI's API (https://openai.com/api/); which, among other things, gives you full (free-daily-API-credit-quota limited) access to an API "playground" frontend offering interaction with the exact same model ChatGPT is powered by — plus other models as well — all without any fixed prompt or forced interaction UX. (In web-dev terms, if ChatGPT is like a REST API, this playground is like a SQL fiddle for the DB that the REST API is backed by.)

(Why does this exist? Because the point of OpenAI's API playground is to test prompts and interaction models for the AI apps you're building yourself on top of their API; and you couldn't very well build apps with your own prompts and interaction models, if OpenAI was already imposing a prompt and interaction model upon you.)

Stable Diffusion is open source, and has already been twisted into positively disturbing dimensions by Reddit etc.