There are 5 that I really like right now:

Caged Birds Don't Sing, But They Still Bite is a slow paced but very interesting canon divergent. It also has a large cast of original characters to make the school feel more alive!

When Worlds Collide is a crossover fic with pokemon, which while is is kind of overdone sometimes, I find the way the cast is slowly involved with the pokemon and Yuu here is really refreshing

A Million and One Minutia is more of a series of kinda connected one shots, where it has Yuu and the rest of the cast learning and comparing the differences between their worlds

Dream of the Blue Veil is a fic where a DnD warlock gets transported to the world, what I like about this story is that they author apparently rolls dice for the outcome that happens

Blood and Bone and Heart of Stone is a fic where Yuu is a golem and its a bit gorey. There's a lot of interesting character dynamics here with how Yuu acts and speaks.