It's about a world where kings are ranked. It shows the story of characters striving for different goals within this ranking system. For example, some might aim for the top rank for power, while others may have more noble reasons like bringing peace and prosperity to their kingdoms.
One idea could be to explore the backstory of a minor character in the Ousama Ranking world. For example, a side character's journey to become a knight. Another could be a fanfic where characters from different kingdoms in the Ousama Ranking universe have to team up for a common goal, like facing a powerful and mysterious enemy that threatens all kingdoms. Also, a story about the daily life of the main character before he started his ranking journey can be really interesting.
First, you should re - watch or re - read the Ousama Ranking to get a fresh feel for the characters and the world. Then, pick a concept or idea that interests you, like I mentioned before. After that, start with a simple introduction of the setting or the main character. For example, 'In the kingdom of [kingdom name], a young boy named [character name] was about to embark on a journey that would change his life, in a world ruled by the Ousama Ranking.'
Not having read the 'ousama game extreme novel', I can only speculate. There could be a young and fearless character who is the central figure, trying to outwit the others in the game. There may be an antagonist who is extremely devious and makes the game even more difficult for the main character. And perhaps there are some other characters with their own motives and secrets, all of which are intertwined in the complex web of the extreme game.
I'm not sure specifically as I haven't seen it. But typically, in a story about a game, there might be a protagonist who is new to the game or trying to figure out its rules. There could also be antagonists who try to manipulate the game for their own benefit.
Typically, there are students who are the main characters in the 'ousama game light novel'. They are ordinary students at first but are thrust into this terrifying game situation.
I don't know the specific main characters in this novel without having read it. But they could be ordinary people who get caught up in this 'ousama game' and have to fight for their survival.