Since I don't know the details of 'the secret grave story', I can't say for sure who the main characters are. But they could be the people who discover the secret grave, like an archaeologist or a curious local.
As there is no information given about this story, it's impossible to say who the main characters are. They could be ordinary people with an extraordinary secret, or they could be fictional characters created for a specific plot.
Given the lack of context regarding the 'bastos secret secret story', we can only speculate about the main characters. If Bastos is a person, perhaps they are the central figure, and there could be friends, family members, or foes around them that are part of the story. Maybe there are also some mysterious figures that help or hinder Bastos in the discovery or protection of the secrets in the story.
I'm not sure as I haven't read it specifically. But they could be people directly or indirectly affected by death, like a gravedigger, a mourner, or someone who has lost a loved one.
In the Grave of the Fireflies original story, the main characters are Seita, a responsible and determined older brother, and Setsuko, his sweet and vulnerable younger sister. Seita takes on the role of a protector. He scavenges for food, finds shelter, and tries to shield Setsuko from the full horror of the war. Setsuko, on the other hand, is a symbol of innocence. Her naivete and her simple joys in the face of such a difficult situation add depth to the story. Their interactions and the way they cope with the war - torn world around them form the core of the narrative.
In 'The Secret in Their Eyes Story', there could be a detective - like character as one of the main characters. This person would be observant and would focus on the eyes of suspects or other people involved in the mystery. There might also be a character who is the keeper of the most important secret. This character would be acting in a way to avoid having their secret discovered through their eyes. And perhaps there is a love interest as well, whose eyes hold a different kind of secret, like a hidden passion or a past relationship.
The main character is a young hero. There is also a female character who becomes an important ally in the adventure. And there are some wise old men who guide the hero on his journey regarding the secrets of Mana.
Since I don't know the exact 'Secret of the Nile Story', I can't say for sure who the main characters are. But they could be explorers, local people living near the Nile, or maybe even some mythical creatures if it's a fictional and fantastical story.
There could be a protagonist who is a young and curious person trying to uncover the secrets of the society. There might also be an antagonist, perhaps an elder in the society who is very protective of its secrets and will do anything to keep them hidden. Other characters could include the members who are loyal to the cause of the society and those who are on the fence about its activities.
Since we don't have more information about the book, the main characters could be anyone from different walks of life. It could be a journalist who is trying to dig out the secret, or it could be a person who has lived with the secret all their life and now the story is about their experiences related to it. There could also be other supporting characters who play a role in either protecting or uncovering the secret.
Since I don't know the specific'secret class story', it could be students who are curious and adventurous. They might be the ones who discover the secret class or are part of it from the start.