The 'amigo brothers' story is about two best friends who are also boxers. They have to face each other in a boxing match. Despite their friendship, they are both determined to win. In the end, they show great sportsmanship and their friendship remains intact.
A fanfic could focus on the relationship between Seiya and Isuzu. Maybe it starts with them having a misunderstanding, like Seiya misinterpreting Isuzu's intentions. But as the story progresses, they gradually understand each other better and their relationship deepens, perhaps leading to a romantic connection.
Since I'm not very well - informed about the 'Isuzu Sento' light novels specifically, it's hard to say for sure. But many light novels often deal with themes like friendship, self - discovery, and adventure.
The main plot is about two friends, Antonio and Felix, who are also boxers. They are very close like brothers but have to face each other in a boxing match. It shows their struggle between friendship and competition.
The main theme is friendship. The two amigo brothers, Antonio and Felix, are such good friends that they do almost everything together. But when they are about to fight in a boxing match, things get complicated. Their friendship is challenged because they both want to win the match. But throughout the story, we see that their friendship is strong enough to survive this tough situation. They don't let the competition destroy their bond, and this shows that friendship is the central theme.