Since it's about monster girls, there could be a variety of main characters. There might be a kind - hearted centaur girl, a mischievous harpy, and perhaps a human male who serves as a bridge between the human world and the world of the monster girls. Each character would bring their own set of traits and story arcs. For instance, the centaur girl could be strong and noble, while the harpy might be more carefree and adventurous.
The main characters in this light novel are likely to be a diverse group. There may be a human character who becomes involved with the monster girls in some way, like a young man who finds himself in a world full of these unique beings. Among the monster girls, there could be a lamia with her snake - like lower body who is wise and mysterious, a slime girl with her own special abilities and a bubbly personality, and a mermaid who is graceful but also has her own challenges in a world that isn't entirely underwater. Their interactions and individual stories would be the focus of the narrative.
I'm not entirely sure as I haven't read every bit of it, but likely there are some key monster girl characters and maybe a human protagonist.