It could also be related to a miscommunication. Dark Mariku misinterprets Anzu's actions or words in the fanfiction and ties her up as a result. This could then be the starting point for a story of them trying to understand each other better and resolve the misunderstanding.
Anzu could also be more calculating. Instead of panicking, she might try to reason with Dark Mariku, asking him why he's doing this and trying to find a way to use his own motives against him to get free.
One possible plot reason could be a misunderstanding. Maybe Draco thinks Hermione has some information that she's not sharing and he ties her up to force her to talk. In some fanfictions, it could be part of a game or a dare within the magical world they inhabit. Another reason might be that Draco is being influenced by some dark magic or a curse that makes him act out of character and tie Hermione up.
One possible reason could be for a power play. Draco, being from a Slytherin family, might want to show his dominance over Harry, who is seen as a hero in the wizarding world. By tying him up, he could be trying to intimidate Harry or gain some sort of advantage in their ongoing rivalry.
One possible reason could be a misunderstanding. Maybe Sasuke has been misled to think Sakura is a threat to him or his goals at that moment. In the Naruto universe, Sasuke has often been on a solitary path filled with suspicion. He might tie her up to keep her from interfering with something he's about to do. Another aspect could be related to some kind of test. He may want to see how Sakura will react in such a difficult situation to gauge her growth as a ninja. It could also be a part of a plan to protect her from something more dangerous, by restraining her movement in a way that he believes is the best for her safety, using the snakes as a means to immobilize her as he is known for his snake - like jutsu.
One possible plot could be that Dark Marik, in his menacing yet strangely alluring way, caresses Anzu as a form of psychological manipulation. He might be trying to gain some advantage in the Yu - Gi - Oh! universe, perhaps using Anzu to get to Yugi. He could be taunting her with his touch, knowing that she is both repulsed by his evil nature but also a bit entranced by his dark power.
One possible plot could be that Anzu is constantly trying to break free from Dark Bakura's mental hold. She might have to face her inner fears and insecurities that Dark Bakura is using against her. Maybe she has to find a way to resist his dark magic and manipulations.
One possibility could be that Percy ties up Annabeth as part of a prank gone wrong. Maybe he was trying to play a joke on her for some past mischief she caused him, but then things spiral out of control and he has to figure out how to untie her before they get into real trouble.
Maybe it's a fanfiction set in a more domestic setting. Marik has to take care of Anzu for some reason and starts using the name 'little Anzu'. The story could show Marik's growth as he learns to be more responsible and caring. Anzu, on the other hand, might initially resist this new dynamic but eventually come to appreciate Marik's efforts. It could also include some cute moments like Marik making Anzu her favorite food and them having heart - to - heart conversations.
It could be that Gaston ties up Kairi and Belle out of jealousy. He's jealous of the attention they receive from others. In the story, while they are tied up, they could recall their own past experiences of facing difficulties. Kairi might think about her adventures with Sora and how she overcame challenges. Belle could think of the time she tamed the Beast. This reminiscing could give them the strength and motivation to break free. They might start by trying to call for help in a way that only their friends would understand, like a special whistle or a call that has a hidden meaning. Then, when their friends arrive, they could all join forces to deal with Gaston.
It could be about Tobi having some serious motives for tying up Sakura. Maybe he's trying to extract information from her, thinking she has knowledge that is crucial for his plans.