McGregor's unruly behavior and his disrespect towards Khabib. He said things that were completely unacceptable. Khabib, being a proud fighter with strong values, couldn't let those remarks slide. So, he took on McGregor in the fight to set things straight and prove his worth in the MMA world.
There was a girl and a boy in a competition. It was a race. The boy was overconfident and made some taunting remarks towards the girl before the race. This made the girl determined to win. During the race, the boy tried to block the girl's path a few times. The girl, not one to be bullied, elbowed him gently but firmly out of the way. In the end, the girl won and the boy was left fuming. But the girl just walked away with a proud smile on her face.
Once, I saw a wife and a mistress have an argument in a park. The wife found out about the mistress and confronted her. The mistress tried to act tough at first, but the wife was full of anger and rightful indignation. The wife started shouting about how the mistress was ruining her family. In the end, the mistress, feeling ashamed, ran away.
Another aspect could be a fanfiction set in an alternate universe where Genkai and Younger Toguro are allies against a greater evil. They could use their combined skills and knowledge to fight off powerful demons. This would show a different side of their relationship, more of a partnership than what we might expect from their normal interactions in the original series.
Jealousy. The wife is jealous of the mistress for stealing her husband's attention and love. And the mistress might be jealous of the wife's legal position in the man's life.
In RWBY fanfiction, the Weiss vs Winter fight can be a display of their different combat styles. Weiss is more about grace and precision with her Glyphs, while Winter, being more experienced, has a more refined and perhaps harsher style. Their fight could also explore their complex relationship as sisters.
In such a fanfiction, perhaps Toguro kidnaps Keiko to use her as bait to lure Yusuke. He might think that Yusuke will come to rescue her no matter what, and then he can have a rematch with Yusuke on his own terms.
One idea could be a crossover with a popular shonen series like Naruto. Toguro could be brought into the Naruto world as a powerful rogue ninja. His immense strength and dark nature would make him a formidable adversary for the Konoha ninjas. Another idea is a crossover with One Piece, where Toguro joins a pirate crew as a fearsome fighter, perhaps with his own hidden motives for being on the Grand Line.
In some fanfiction, they could be involved in a tournament together. Genkai as a mentor figure guiding Younger Toguro through the challenges of the tournament, teaching him strategies and how to control his emotions during the battles. This would show their relationship evolving in a high - stress environment.
Jealousy is a common reason. For example, if one wife has a more luxurious lifestyle or gets more attention from others. Another reason could be competition, like competing for a limited resource such as a particular job opportunity in a small community where their husbands work at the same place.