It could be about the relationship between the protagonist and their senpai. Maybe it involves the daily interactions, the growth of their bond, and some emotional experiences like friendship or a budding romance.
The main characters are probably the protagonist and their senpai. There might also be some supporting characters like the protagonist's friends or classmates.
It's about a story where the senpai is a bunny girl. Usually, it might involve some kind of unique relationship, perhaps a romantic or a very special friendship. It could also include elements of school life and the reactions of others to this bunny - girl - like senpai.
The main character is likely the senpai who is a bunny girl. And there must be a protagonist who has a relationship with her, could be a fellow student or someone close to her in the story's setting.
I'm not sure if 'the senpai a seinfeld visual novel' is popular. Since I haven't heard much about it, it may not be widely known or it could be a relatively new release that hasn't gained a large following yet.