There's no way to tell exactly without reading it. However, it might have a local who has lived near the ghost tree all their life and knows some of its secrets as one of the main characters. And perhaps a newcomer to the area who is drawn to the mystery of the tree could also be a main character.
Since I'm not familiar with the 'Ghost Tree Graphic Novel', I can only speculate. It could have a group of kids as the main characters. They might have heard the spooky tales about the ghost tree and decide to go on an adventure to find out the truth. There could also be an old hermit - like figure who has some knowledge about the tree's true nature and plays a crucial role in the story as one of the main characters. The interactions between these different types of characters would then drive the plot forward in the graphic novel.
I don't know for sure as I haven't read it. But it could have a young adventurer as a main character who is intrigued by the ghost tree.