Well, it could be that Toguro has some ulterior motives for kidnapping Keiko. Maybe he believes she has some special power or knowledge that he can use for his own gain. So he takes her to a secret location and tries to force her to reveal what he wants.
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.
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.
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.
Yusuke could use his spirit detective skills to track down Keiko. He might fight his way through Sakyo and Toguro's minions to reach her.
One possible plot could be that Keiko is caught in the crossfire of a demon battle that Yusuke is involved in. Yusuke, being a spirit detective, has many enemies. Maybe a powerful demon targets Keiko to get back at Yusuke. After her death, Yusuke could go into a deep state of despair and vow revenge. He might journey to the spirit world to find a way to bring her back, facing numerous challenges along the way.
In one scenario, Hiei might kidnap Keiko to use her as bait to draw out Yusuke. He could be forced by some powerful enemy who wants to get revenge on Yusuke. Hiei, being a rather complex character, might not be entirely happy about this but feels he has no choice. He would keep Keiko in a hidden location, perhaps in the demon world where it's hard for Yusuke to reach easily.
One possible plot could be that Rando is a jealous rival of someone close to Keiko. He kidnaps her to try and force her into a relationship with him. Keiko, being a strong - willed character, tries to outwit Rando at every turn during her captivity.
In a more out - of - the - box plot, Matpat could be kidnapped by an interdimensional being that is offended by his theories about certain game universes. Matpat then has to convince the being that his theories are just speculation and try to find a way back to his own dimension, all while trying to understand the strange new world he's in which is filled with elements from different games he's analyzed.
It could be that Gohan is kidnapped by a group who wants to study the Saiyan physiology. They might be scientists from a different planet or a secret organization on Earth. They take Gohan in order to run various tests on him, not realizing the danger they're in if Gohan manages to break free. And his friends and family then have to go on a mission to rescue him.
In the fanfiction, Arcee could be kidnapped because she has some crucial information. Maybe she discovered a secret plan of the Decepticons and they kidnapped her to keep her from sharing it. The Autobots would need to find her quickly and also figure out a way to stop the Decepticons' plan without Arcee's help at first.
One possible plot could be that Aladdin is kidnapped by a powerful sorcerer who wants to use his knowledge of the magic lamp to gain more power. His friends, Jasmine and Genie, then have to embark on a dangerous journey to rescue him. They might face various obstacles along the way, like magical traps and other evil minions.