Maybe an old enemy of the hero agency where Present Mic works. They could be seeking revenge on the agency and think kidnapping Present Mic is a good way to start their attack. They might have some past grudges against the agency's policies or actions that involved Present Mic.
There's also the possibility of a group of villains working together. For example, a group of villains who specialize in different areas like one being good at stealth (for the kidnapping part) and another being good at negotiation (to deal with the demands they make after the kidnapping). They could have a common goal of undermining the hero society by targeting Present Mic.
It could be a new villain who is trying to make a name for themselves by targeting a popular hero like Present Mic. They might see him as an easy target to get attention.
In another scenario, it could be a case of a deranged fan who kidnaps Present Mic because they think they can have him all to themselves. This could lead to a psychological exploration of the kidnapper's motives and how Present Mic tries to reason with the fan and escape, while the other heroes are on their way to save him.
The villain could be a jealous ice - mage who wants Elsa's powers all to himself. He sees Elsa as a threat to his own dominance in the world of ice magic.
A present mic fanfiction could focus on his relationships with other heroes. He seems like a really friendly and outgoing guy, so it could be about his adventures with Eraserhead. They could be solving a mystery together in a noisy city, with Present Mic using his voice to disrupt villains while Eraserhead takes them out.
A theme could also be his heroic deeds. Fanfictions could be written about him saving a large group of people from a powerful villain using his sonic powers in creative ways, like creating a sonic shield to protect them or using his voice to confuse the villain into making mistakes.
A rogue ninja from another village who is jealous of Ino's talents and the reputation of her village could be the villain. This ninja might think that by kidnapping Ino, they can bring down the morale of her village and prove their own superiority.
In a more fantastical setting, it could be a magical being who has some sort of vendetta against Peter or Michelle. Maybe they accidentally disrupted some magical ritual or offended the being in some way, and now the being wants to use their kidnapping as a form of punishment or to get something from them.
A mad scientist - type character could be the villain. He might be obsessed with creating the perfect virtual being and sees Hatsune Miku as the key. So, he kidnaps her to run all kinds of experiments on her code. He wants to extract her unique singing ability and transfer it to his own creations.
A plotline could revolve around their family life. Maybe they decide to adopt a child with a quirk that's difficult to control. They'd have to use their combined skills and experience as heroes and as a couple to help the child. It could show how their marriage is not just about their love for each other, but also about their shared sense of responsibility towards others. And of course, there could be some really cute family moments.
Well, 'bnha' is likely referring to 'My Hero Academia'. A 'dark' fanfiction about Present Mic could explore his character in a more sinister or complex light. It might involve him facing moral dilemmas or being part of a darker storyline within the My Hero Academia universe. Maybe it could show his past traumas influencing his actions in unexpected ways.
Often, the dynamic between Present Mic's energetic and loud personality and the Reader's more relatable or 'normal' perspective creates interesting interactions. The Reader can be written as being in awe of Present Mic's hero status at first.