The story is one of the core aspects for visual novels. This article will focus on the early planning stages of creating a visual novel.
In the early stages when developing a visual novel it is best to have an idea of what the game will be about. That's why I suggest writing out the story and dialouge draft before moving on to the next step. It makes the story stay on track and prevents plot points from being forgotten.
There are various tools when outlining the story for a visual novel. There are both free and paid software to use for writing. My personal choice is Twine, it is a open source tool for writing interactive stories. I use Twine to draft and map out stories before moving to Renpy for the next steps.
Going back and making changes to the story is likely going to happen when adding dialouge to the game. An example is going back to change dialouge to flow more easily.
Depending on what the visual novel is about. The story could be long or short, simple or complex, the duration of a story varies. It could take a week, to a few months, or maybe up to a year to write and edit your story.
Having another pair of eyes to look over the story to proofread is a good check to make sure the story flows as the game progresses. Another option is to ask for feedback to help improve the story.