I'm not entirely sure as the statement is rather unclear. It could potentially be a fanfiction where a character named Percy is depicted as being drunk. But without more context, it's hard to say exactly.
Grover could also be a main character. He might be at the scene when Percy gets drunk and try to use his nature - related powers to sober Percy up. Grover could also provide some comical relief with his reactions to Percy's drunken state, like his horrified expressions or his attempts to herd Percy like he would a wild animal.
One possible plot could be Percy getting drunk and accidentally revealing his true feelings to a friend or love interest. For example, he might finally admit his long - hidden admiration for Annabeth while in a drunken state.
Snape is always complex. In this situation, he would be conflicted. On one hand, he has his long - standing dislike for Harry (or rather, his connection to James). On the other hand, as a teacher, he has a duty to take care of a student in distress. Drunk Harry would be a bit clumsy and giggly perhaps. His judgment would be clouded, and he might see Snape in a different light, not as the enemy but as someone who could help him, which could start to shift their relationship dynamic in the fanfiction.
It could be a fanfiction where the sakura, being a symbol of beauty and transience in Japanese culture, is associated with a drunk character. Maybe the character gets drunk under the sakura trees and has some sort of self - discovery or has a series of strange encounters. For example, they might meet an old acquaintance or a magical being, and the drunk state adds an element of unpredictability to the story.
Some characters might try to quickly annul the marriage. They could be embarrassed and want to pretend it never happened. For example, Weiss might be very concerned about her family's reputation and immediately seek legal means to end the marriage.
I don't know for sure as I haven't read this particular fanfiction, but usually in fanfiction, Percy could be a character from a popular book, movie or TV series.
I'm not sure who Percy specifically is without reading the fanfiction. It could be an original character created by the author, or perhaps a reimagined version of a known character from a particular franchise that the fanfiction is based on.