Since I'm not familiar with a specific 'Passion Yuuji' novel, in general, a novel might have unique characters. Maybe the characters in this novel have strong emotions and passions that drive the plot forward.
I'm not sure as I haven't played this visual novel specifically. There could be a lot of different interactions between characters in a visual novel, but without experiencing it first - hand, I can't say for certain.
He might be depicted as confident. In a visual novel, this could be shown through his interactions with other characters, where he takes the lead in conversations or situations.
Toge Inumaki is important too. His special cursed speech ability makes him stand out. Also, the principal of the school, Masamichi Yaga, is likely to be important as he is in a position of authority and has an influence on Gojo and the other students. There could be other characters like the members of different clans that also play roles in the complex web of the story.
No, there are no sex scenes in the Labyrinth of Grisaia Yuuji story. It is a visual novel that focuses more on the story, character development, and the exploration of relationships in a non - explicit way.
Well, Kazami Yuuji in a visual novel can have various roles. He could be involved in different story arcs, for example, a love story arc where he has to deal with his feelings for other characters. His design in the visual novel might also be quite distinct, with unique hair color, clothing style that gives players an idea about his personality at first glance. And his actions and decisions throughout the visual novel are what make the story interesting and engaging for the players.