Definitely Midoriya. He's such a central figure that it's easy to imagine how hypnosis could play into his story. He could be hypnotized to doubt his own abilities or, on the flip side, be hypnotized to unlock new levels of his quirk. Ochaco Uraraka is another character who could be involved. Her zero - gravity quirk could be manipulated through hypnosis. For example, she could be hypnotized to lose control of her quirk in a dangerous situation or be made to use it in a more powerful and unexpected way.
Well, Todoroki Shoto is a likely candidate. His complex family history and his dual - natured quirk make him an interesting subject for hypnosis in fanfiction. Hypnosis could be used to explore his relationship with his father more deeply or to unlock new aspects of his ice and fire powers. Momo Yaoyorozu, with her creation quirk, could also be involved. Hypnosis might be used to either enhance her creativity in using her quirk or to disrupt it, leading to all sorts of interesting scenarios in the fanfiction.
Naruto himself is often involved. His strong will and determination could make him either a target of hypnosis or someone who has to resist it. Sasuke is also a likely candidate, given his powerful doujutsu, the Sharingan. Hypnosis could potentially be used to manipulate his actions or unlock hidden aspects of his Sharingan powers.
Harry Potter himself is often involved. Writers might explore how he could be hypnotized to face his inner demons or unlock new powers. Hermione is also a popular choice as her intelligence could be enhanced or her memories explored through hypnosis.
Obviously, Izuku Midoriya will be the central character. His friends from U.A. High like Ochaco Uraraka and Tenya Iida are likely to be involved. They would be there to support or oppose Izuku depending on the nature of the spiral he's in. Also, All Might might play a role as Izuku's mentor, guiding him through whatever challenges the spiral presents.
Hermione Granger might also be a key character. She's so intelligent that she could be the one to study and figure out how to control or counter hypnosis powers. For instance, if there's a new threat in the wizarding world related to hypnosis, Hermione would be the one delving into the library to find solutions. And of course, there could be original characters created specifically for these fanfictions. These could be new students at Hogwarts who have a natural affinity for hypnosis powers and get involved in all sorts of adventures with the well - known Harry Potter characters.
Issei is often involved as he is one of the central characters in the Highschool DxD universe. His character can be greatly influenced by hypnosis, either being the one using it or being affected by it.
I think the students like Kaminari and Sero would be involved. Kaminari with his goofy personality might initiate some pranks, and Sero could use his tape quirk to set up some elaborate prank setups. Also, the teachers like Aizawa could be involved. He might play a prank on the students to teach them a lesson in a rather unorthodox way. Another character could be Todoroki. His rather stoic nature could be a great contrast to the chaos of a prank.
Percy Jackson himself is often a central character in such fanfics. Since he's the main protagonist of the original series, it's natural for him to be involved in hypnosis - related plots. Annabeth Chase also frequently appears, as she has a close relationship with Percy and would be involved in trying to help or understand him during a hypnotic state.
Naruto himself is often a main character. Since he's the hero of the original series, it makes sense that he would be involved in fanfiction related to heroics and something like special water. He might be the one to discover the water's power.
I think Icarus is the central figure in this fanfiction. But characters like Midoriya Izuku would also be important. Izuku's journey as a hero - in - training could be intertwined with Icarus'. Maybe they become friends or rivals. And villains from My Hero Academia, such as Tomura Shigaraki, could also be main characters. His evil plans might be affected by or target Icarus, adding more drama to the story.
Todoroki is also a popular choice. His complex backstory and powerful quirk make him an interesting candidate for quirk swaps. Swapping his quirk with someone like Momo, who has a creation quirk, could lead to really unique storylines.