Since we don't know the full story, it's hard to say for sure. But it's likely that the main character is the 'rose beetle man' himself.
I would assume the main character is the 'rose beetle man'. He is the one who gives the story its name. It's possible that the story is told from his perspective, and all the events and other characters in the story are related to him in some way. For example, there could be other characters like his neighbors who are bothered by the rose beetles that he seems to have an affinity for, or there could be a scientist friend who helps him study the beetles. But at the heart of it, the 'rose beetle man' is the main focus.
I'm not sure exactly as the story isn't widely known to me. But perhaps it could be about a man who has some special connection with rose beetles, like he might study them, or they play a role in his life in some unique way.
Since I don't know the specific 'beetle boy story', the main character is likely to be the boy himself. There might also be some beetles as important characters, perhaps a wise old beetle or a brave young beetle that helps the boy.
As mentioned before, if we assume it's related to the Star Wars we know, the main character would likely be Rose Tico.
As we don't know the details of 'the man story', the main character is simply 'the man' in question.
The main characters are the beetle and the turtle, as it's a story about them.
Since it's called 'beetle boy novel', the beetle boy is surely a main character. He could be joined by other characters such as a mentor figure who helps him understand beetles better. There might also be antagonists, perhaps people who are against the beetles or what the boy is trying to do with them. Maybe there are some fellow beetle enthusiasts as well who become his friends along the way.
Since we don't have much information about the specific'man with 2 faces story', it's hard to determine the main character precisely. It could be an unnamed man who is simply used to represent the concept of duplicity.
Since we don't have the details of the story, the main character is simply the tattooed man. He is likely at the center of whatever events or themes the story revolves around.
As we don't know the details of this story, the main character is presumably the man on the train.
There's no way to tell without more details about the story. It could be a named character like John or Tom who finds himself in a situation that leads to him being the 'hooked' one. Maybe he's a fisherman and he gets hooked in a freak accident, then he becomes the main character of this 'hooked man story'.