If such a fanfiction existed, it would probably be quite controversial. The relationship between Harry and Snape is complex in the original books. A plot like this would require a lot of background building to make it seem plausible. It might involve some kind of alternate universe where the rules of their relationship are different. The writer would have to be very creative in justifying why Harry would make such a request and how Snape would react.
It would be a very strange and unique piece of fanfiction. Given the nature of the relationship between Harry and Snape in the original series, which is often tense and full of animosity, this scenario would completely flip the dynamic on its head. It would likely be a very character - driven piece, exploring new facets of their personalities.
I'm not sure if there is a specific fanfiction with that exact plot. Fanfiction is a vast world, and while there might be some out there that explore unique and unexpected scenarios between Harry and Snape, this one seems rather unusual. You could try searching on popular fanfiction websites like Archive of Our Own or Fanfiction.net.
Harry is likely to be angry at first. He has always had a tense relationship with Snape, and this act of spanking would seem unjust and humiliating to him.
Another way Snape could comfort Harry is by standing up for him in certain situations. Maybe when other teachers or students are being unfair to Harry, Snape steps in and defends him. This act of protection can be a great source of comfort for Harry, as it shows that someone is on his side even if they have had a rocky relationship in the past.
In some fanfictions, Snape might use his advanced knowledge of potions to brew a special healing elixir for Harry. He could also use his magic skills, like a complex spell specifically designed to mend Harry's wounds, whether they are physical or emotional.
Snape would probably be quite surprised at first. Hermione is known for her academic prowess and self - sufficiency. His reaction could range from being dismissive, thinking she should be able to solve her own problems, to being intrigued by the nature of her request. If it's something related to the dark arts or a mystery in the wizarding world, his interest might be piqued, but he'd still be guarded in his response. He might even try to use her request as a way to gain some advantage or information for himself.
In fanfiction, Snape teaching Harry Occlumency is often a very intense and complex relationship. Snape's own mixed feelings towards Harry add layers of drama. His strict teaching methods sometimes seem cruel but are also necessary to force Harry to master Occlumency. Harry, on the other hand, is often resistant at first, not fully understanding the importance and also being put off by Snape's attitude.
Sure, the Harry Potter fandom is huge and full of creativity. Writers might come up with a story where Harry is Snape's master for various reasons. It could be due to a prophecy or a magical bond that no one expected. In this kind of fanfiction, we might see Snape having to follow Harry's orders, which would be a complete reversal of their normal relationship in the original series. This could lead to some very intense and dramatic storylines.
One possibility could be that in this fanfiction, Snape takes Harry for some sort of training or protection. Maybe Snape realizes that Harry is in greater danger than Dumbledore anticipates and decides to take matters into his own hands. He might take Harry to a secret location to teach him advanced magic or to keep him away from the prying eyes of Voldemort's followers.
Rather than focusing on this specific and somewhat unusual type of fanfiction, you might want to explore more general Severus Snape fanfictions. There are many great ones that delve into his character, his relationships in the wizarding world, and his backstory. These can be found by simply searching for 'Severus Snape fanfiction' on popular platforms, which will give you a wider range of engaging stories to choose from.
Another reason might be that Harry is suspected of sneaking around in areas where he's not supposed to be. Snape, as a vigilant teacher, may punish Harry to maintain discipline in the school. He may think Harry is up to something related to the ongoing dangerous situations in the wizarding world and wants to keep him in line.