For the first prototype, I plan on providing the manuscript of the prologue as well as a short synopsis of the rest of the visual novel. Although there will not be any visuals, the plot is what the bulk of the visual novel will be. From this I plan on asking questions to determine if the story and dialog is easy to follow as well as gauging whether or not the actual story is interesting and making adjustments accordingly based on feedback.
The second prototype will be more visual based, I will bring rough sketches and character profiles. I will be asking questions on the visual aesthetics like – Does it look good? Do the various styles fit? The character profiles will include their design as well as their personality and a short bio about them. I’ll be asking questions on what they think of the design, what do you like/dislike about them, and do you think they would work together?
The third prototype will bring the first two together into a short demonstration of a part of the visual novel. This is to determine how the visuals and story actually work together. I will also be asking if the controls are easy to use and if the visual novel flows well. I will also be asking if the sound effects and background music complement or take away from the experience.
Good job with your plan–your first prototype covers the foundation of your project, and the others build from there, so you should get helpful feedback on all three.
When collecting feedback, be sure to ask follow-up questions as needed–if someone says they like something, dig a little deeper to find out why, what aspect, etc.