Since I don't know the specific 'grass graphic novel', I can't say for sure. But they could be people who live in a grassy area, like farmers or herders. Or maybe there are magical creatures that inhabit the grasslands.
I'm not sure exactly, but there might be a protagonist who ventures into the tall grass first.
The main characters are Deanie and Bud. Their relationship is central to the story.
It's possible that there are characters who are trying to find a solution to the problem of the grass dying. Maybe there's a scientist character who is researching the cause, or a community leader who is trying to rally people to take action. Without reading the book, it's hard to say for sure.
I'm not entirely sure about all the main characters, but there are some characters who are central to the story in that small town.
Given the vagueness of 'grass woman stories', the main character is the woman, but depending on the type of story, there could be antagonists too. If it's a story about a woman protecting the grassland from being destroyed, then the people or forces trying to destroy it could be the antagonists. Or if it's a more spiritual story, there could be spirits or deities associated with the grass that are important characters in the story.
Since I don't know the story, I can't say for sure who the main characters are. But they could be scientists who are studying the grass, or perhaps children who discover something unusual about the grass in their backyard.
Since we don't know the exact story, it could be the kings themselves. They are likely the central figures.
I'm not sure without reading the actual story, but it could be a protagonist who is the victim of the'snake in the grass' and the antagonist who is the sneaky, untrustworthy character represented by the snake.
Cal Demeter is one of the main characters. He is a young man who gets drawn into the mystery of the tall grass.
A nature - loving hippie could be the main character. They are always seeking a connection with the earth and are often found barefoot on the grass, meditating or just enjoying the feel of the grass beneath their feet.