I'm not sure of the exact significance of '23 percent' in it. It could be an arbitrary number the author chose to mark a certain part of the fanfiction.
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.
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.
His friends like Kuwabara and Kurama might also join in the rescue. Kuwabara with his tough fighting spirit and Kurama with his cunning and powerful abilities could be a great help in getting Keiko back from Toguro.
Well, perhaps in this fanfiction, Sakyo and Toguro kidnap Keiko because they think she has some special power or knowledge. Maybe they believe she can lead them to a powerful artifact. Keiko, being a strong - willed character, tries to resist them and find a way to escape. Meanwhile, her friends are desperately searching for her, and they end up having to team up with some unexpected allies to take on Sakyo and Toguro.
In a crossover with the Fate series, Saber could be paired with Toguro. Saber's sense of honor and her noble fighting style would clash with Toguro's brute force and underhanded tactics. It would create a really interesting dynamic, whether they are on opposing sides or forced to work together for some greater purpose.
Fanfiction related to '7percent solution' is likely to be centered around the concepts and characters of the source material. It might play with the mystery and intrigue aspects of the original. Writers could create scenarios where the main characters face different challenges or make different choices. They might also explore the historical and cultural context of the story more deeply, perhaps adding more details about the time period in which the story is set, or even changing some aspects of the setting to create a unique take on the original narrative.