One popular edo period visual novel could be 'Hakuoki'. It features a story set in the Edo period, with elements like samurai, historical events, and complex relationships. The characters are well - developed, and the art style often captures the essence of the era.
First, do a lot of research on the Edo period. Read historical books, watch documentaries about that era. This will give you a solid base for your story. Then, think about the characters you want to include, like samurai, merchants, or geisha. Sketch out their personalities and backstories.