Manga/Anime/Manhwa/Manhua where the character pretends that they're bad at something (ex. sports or singing or i dunno) but are actually pretty good... they can pretend because they are too shy.. or something happen in their past.... etc.
For ex; Red Lion - she pretends (for a while) that she's just a weakling but the truth is she's really strong and good at fighting Fly High! - she pretends she's weak... but she was training in the mountains for 6 years so she's pretty strong Superior (my all time best thing to read <3 <3) - she pretends she's a weak cat spirit and can't do anything... but she's actually the queen of all demons~!!!!!!!
Gokusen - The main character hides her skills at fighting and her family background because she's a teacher. ...That and she will be fired if they actually find out she's the next heiresss to a yakuza family. Lots of comedy and character development.