At the start, Harry would be angry and feel that he's been wrongly accused or punished. But as the detention goes on, he might start to realize that there could be more to Snape's actions. He might become more curious about Snape's motives and start to pay more attention to what Snape says and does during the detention, rather than just being defiant.
Harry would probably be quite resentful at first. He might think Snape is just being his usual unfair self. So, he would be sulky and do the tasks reluctantly.
Harry would initially be in a bad mood, muttering under his breath about how unfair it all is. However, as he has no choice but to endure the detention, he would gradually focus on the tasks at hand. He might find himself learning something new about Potions or about Snape. Maybe he'd notice a flicker of something in Snape's eyes that makes him wonder if there's more to Snape than just the mean teacher he always thought him to be.
Snape's reaction could also be one of extreme caution. He would be constantly on guard, worried that Harry might discover some of his secrets or that Voldemort's supporters might target Harry while he's in his care. So he would be very vigilant, but this might also lead to some over - the - top reactions when Harry does something even slightly out of the ordinary. However, over time, this vigilance could turn into a form of care as he gets used to Harry being around.
Well, Harry could be forced to clean the Potions classroom during detention. Snape might make him scrub every cauldron by hand while muttering about how clumsy Gryffindors are. Harry might accidentally spill a potion ingredient, which makes Snape even angrier and gives him more tasks to do, like sorting out all the potion ingredients in the store cupboard.
Snape would probably be very conflicted. On one hand, he has a long - standing grudge against James Potter, Harry's father. But on the other hand, he loved Harry's mother, Lily. So, he might be cold at first, but then his sense of protecting Lily's son could kick in. He would likely be very strict with Harry, as he is with all his students, but also secretly keep an eye on him to make sure he's safe.
The other Hogwarts students would have a wide range of reactions. Some might be shocked and gossip about it. Neville, for example, might be sympathetic towards Harry. Draco Malfoy could use it as an opportunity to taunt Harry, but at the same time be a bit envious of the attention this situation brings. The teachers would also have different responses. McGonagall might be worried about the impact on Harry's education and future.
He'd probably be annoyed. Snape is a serious wizard and he might think fanfiction is a silly Muggle - influenced concept.
Snape would likely be initially suspicious. He's not used to Harry coming to him for help or sharing secrets. But once he realizes the seriousness of what Harry is saying, he might start to see Harry in a new light. He could be grudgingly helpful, still maintaining his cold exterior but secretly starting to feel a bit more protective of Harry.
Snape would likely be angry at first. Harry has always been a source of trouble in his eyes, and running away would just add to that perception. He might mutter some sarcastic remarks under his breath about Potter's irresponsibility.
It could change in a more positive way. In detention, they might have to rely on each other to get through Snape's tasks. If they are made to work on a complex magical experiment, they would need to communicate. This communication could break down some of the barriers between them. Maybe they start to exchange a few friendly words outside of detention, slowly building a more amicable relationship.
The Slytherin house would probably be outraged. Snape is one of their own, in a sense. They would demand justice for Snape and might even use this incident to fuel their long - standing rivalry with Gryffindor. There would be a lot of tension and conflict within the Hogwarts community as a result of this act.
The fandom's reaction would be quite mixed. Some fans, who are more open to extreme and creative interpretations in fanfiction, might find it an interesting and bold take. However, the majority would probably be horrified. Snape is a beloved and complex character, and this idea of him being aroused by Harry fanfiction is so far from what J.K. Rowling created. It could lead to a big debate within the fandom about the limits of fan - created content and how it should respect the original source material.