It could also be a secret organization within the Naruto universe that we don't know much about in the original story. This organization might be aware of some hidden prophecy or potential in Naruto related to the Nine - Tailed Fox. They kidnap him with the intention of either preventing that potential from being realized (if they see it as a threat) or using it for their own mysterious ends.
Orcs would be a likely kidnapper. They have a long - standing enmity with the elves, and Legolas being an important elf, would be a valuable captive. They could either want to torture him for information or use him as a bargaining chip with the elves.
In a fanfiction, it could be a shadowy organization. They might have heard rumors about Raven's unique powers and decided to take her. This organization could be researching ways to gain superhuman abilities and believe Raven holds the key. Or it could be a deranged fan of Raven's powers. He might be obsessed with her and think that by kidnapping her, he can have her all to himself. Additionally, a vengeful spirit from Raven's past could be the kidnapper, seeking revenge for something she did long ago.
It could be an obsessed fan. You know, someone who has taken their admiration too far. They might think that by kidnapping Liv and Maddie, they can have them all to themselves and be part of their exclusive world. This type of kidnapper would be really unpredictable as they are acting out of an extreme and abnormal form of love.
It could be a rogue ninja who wants to sell Naruto to the highest bidder. There are always those in the Naruto world who are after power and money.
It could be a rival faction. In the Rance universe, there are often different groups vying for power or resources. A rival faction might see Harry as a threat or an opportunity and kidnap him to gain an edge.
One possibility is that the kidnapper is an ex - partner or an ex - friend who has turned bitter. They might feel betrayed by the girl with glasses in some way and think that kidnapping her is the best way to get back at her. Another likely candidate could be a character from a parallel story or an alternate universe who has some sort of vendetta against the girl. For instance, if there are different factions in the fanfiction world, and the girl with glasses is on one side, someone from the opposing side might kidnap her to gain an advantage. Additionally, it could be a self - proclaimed vigilante who believes the girl is involved in something wrong and takes it upon himself to 'punish' her by kidnapping her.
It could be someone Reid put away in the past. Maybe a criminal who has held a grudge against him ever since and has now found an opportunity to kidnap him for revenge.
It could be a jealous rival. Maybe someone who is envious of Felicity's intelligence or her relationships. Without her glasses, this person might think she's more vulnerable and easier to manipulate or hold hostage to get what they want.
It could be Orochimaru. He is always on the lookout for powerful specimens to experiment on or train in his ways. Naruto, as the son of the Fourth Hokage, would be an extremely appealing target for him at birth.
It could be a jealous coworker. Maybe they feel that Kaoru is getting all the attention or a promotion they wanted. Another possibility is a patient who has become obsessed with Kaoru during their treatment. Or perhaps it's someone from Kaoru's past who has a grudge against her.