The school janitor could be the main character in a school detective story. He knows every corner of the school. He might notice things that others don't, like a small hole in the wall that seems to be freshly made and might be related to a mystery of missing art supplies. He has access to all the areas, including the basement and storage rooms where important clues could be hidden.
A teacher can also be the main character. A history teacher, for instance, might be interested in solving a mystery related to an old school artifact that has disappeared. With his knowledge of history and research skills, he can dig into the past of the school and interview old teachers and alumni to find out what happened to the precious item.
The main character of 'the invisible man detective story' is the invisible man. He is a character full of enigma. His invisibility gives him an advantage in some ways but also makes him a target. The detective in the story has to figure out his motives, his past, and how to deal with his invisible presence. The invisible man's actions drive the plot forward as the detective tries to track him down and understand what he is up to.
Often, it's a student who stumbles upon the mystery. For example, a curious new student who isn't afraid to explore the school's hidden corners.
Detective Conan was a Japanese mystery novel, in which the protagonist was a high school detective, Kudo Shinichi. He was a famous detective who often solved all kinds of mysterious cases. In addition to Shinichi, there were other important characters such as Maori Kogoro, Conan's childhood sweetheart Heiji, and Haihara Ai.
The main character is most likely the boy detective. In stories set in Oz, there are often unique characters, and this boy detective must be special too. He might be a human from our world who somehow gets transported to Oz and this otherland, and his detective skills are what set him apart. He could be brave, intelligent, and curious, which are all great qualities for a detective in such a fantastical setting.
The main character could be a small spider. It's trying to find a place to build its web in the school and has all kinds of adventures while doing so.
A curious journalist. They are always looking for a good story and an abandoned school is full of potential.
The main character could be a student athlete. He is constantly under pressure from the coach who is 'ballbusting' him to improve his performance. The athlete has to balance his studies, his social life, and the intense training regime.
Without more information about the 'chrisland school girl story', it's impossible to say who the main character might be. It could be any girl in the Chrisland school who has a story worth telling, whether it's a student who has made a significant impact on the school community or a girl who has had an extraordinary personal experience within the school.
Most likely, the main character would be skydoesminecraft himself in this story.
Obviously, it's Kristy. Since the story is named after her, she is likely the central figure around whom all the events in the after - school time revolve.