The aliens themselves can be considered main characters in a way. They are the catalysts for all the events in the story. Their different form of communication and perception of time create the central conflict and mystery that Louise and the other humans have to figure out.
I'm not entirely sure, but there could be a young protagonist who is the center of the story. Maybe a mentor figure as well, someone who guides the main character through different challenges.
It's possible that there are a group of friends or family members as main characters. Their interactions and how they support or hinder each other's enjoyment of life could be central to the story.
I'm not sure as I haven't read the novel. But it could be a pair of characters, perhaps a protagonist and an antagonist. The antagonist might be the one who claims 'your life is mine', while the protagonist is the one whose life is in jeopardy.
There could also be a detective - like character who is running for his life while trying to solve a mystery. He might be getting too close to the truth in a case involving powerful and dangerous people, and now he has to use his wits not only to solve the mystery but also to stay alive while being chased by the bad guys.
There are many possibilities for the main characters. It could be a detective who is on the run because he has uncovered a conspiracy within his own department. Or it could be a family that has to flee their home due to some external threat, like an invading army. Without more information about the story, it's hard to say exactly who the main characters are.
Well, Naruto is most likely one of the main characters since it's a Naruto fanfic. He's the central figure in the original series, so it's very likely he'll play a major role in this fanfic as well. Sasuke might also be a main character, as their relationship is a crucial part of the Naruto story.
Since I don't know the specific '25 to Life Story', I can't say for sure who the main characters are. But if it's about a prison - related story, there could be inmates, prison guards, and maybe family members of the inmates.
The main character in 'Story of Your Life' is a linguist. She is intelligent, curious, and determined. Her inquisitiveness drives her to study the heptapod language despite the many challenges. She is also a complex character as she has to deal with the implications of learning a language that changes her perception of time.
There's Emily, a young and independent artist. She's full of creativity and has a passion for painting. And then there's James, a successful businessman. He's a bit reserved at first but has a kind heart.
I don't know as I haven't read the novel. It could be a young protagonist who is trying to make sense of their dreams.