There's a fanfic called 'Nagisa's Assassin's Creed'. It shows Nagisa in a world of assassins, where she has to navigate through various challenges and prove herself. The story has a lot of action scenes that highlight her badassery.
I'm not entirely sure specifically about 'nagisa no visual novel' without more context. It could potentially be a visual novel centered around a character named Nagisa. Visual novels often have storylines involving relationships, personal growth, and various adventures.
In the 'Assassination Classroom' series, Nagisa is male. In fanfics, while some might play with the concept in creative ways like gender - bender scenarios for the sake of unique storylines, traditionally Nagisa is a male character.