Creating an adult visual novel involves several steps. First, you need a good story concept. Outline the plot, characters, and their relationships. Then, you need to gather or create the visual assets like character sprites and backgrounds. For the programming part, you can use software like Ren'Py which is popular for visual novel creation. However, please note that creating and distributing adult - themed content may be subject to various legal and ethical restrictions in many places.
To create an adult visual novel, start with a strong narrative. Decide on the genre, whether it's romance, mystery, etc. within the adult context. Next, you'll have to think about the dialogue. It should be engaging and in line with the characters' personalities. Regarding the visuals, you can either draw them yourself if you have the skills or hire an artist. But keep in mind that adult visual novels are often restricted in terms of distribution and may not be acceptable in all communities.