One potential unique feature of the 'ao oni visual novel' could be its storytelling approach. It might blend traditional Japanese horror elements, which are often associated with 'oni' (demons), with modern visual novel mechanics. For instance, instead of a linear story, it could have a branching narrative that is deeply influenced by the player's relationship with the 'ao oni' character. The visual elements, too, might be unique. It could use a color palette that emphasizes the 'ao oni' theme, such as lots of blues and dark shades to create a sense of mystery and danger. And the character development might be centered around the characters' psychological responses to the 'ao oni', which could be a different take compared to other visual novels.
Some possible unique features in 'ao oni visual novel' could be its use of sound. Since it's about something like 'ao oni' which might be a bit spooky, the sound effects and music could be really immersive, creating a very eerie atmosphere. Also, the character interactions might be unique. If the 'ao oni' is a main character or an antagonist, the way the other characters interact with it could be different from other visual novels. For example, the dialogue choices when facing the 'ao oni' could be very intense and have high - stakes consequences.