Do you like Eruri? (ErwinxLevi from attack on Titan) This is one classic fic of them!
(It's an au so no need to know plot of aot, though you will miss on some character dynamics)
https://archiveofourown.org/works/4719944/chapters/10783484#main
It's one of the best fanfiction I've ever read!
For general, there is one from Mob Psycho (it's sti...... reply
