Basically, Drama where a character needs to hide his power/skill - then, when the big reveal happens, and the other characters realize he was really awesome all along.

Possibly...

The Atypical Family Bok I Na is kind of looked down upon/ignored until it's revealed she's had a superpower all along

 Love Game in Eastern Fantasy ML hides his identity/powers as a demon 

Love of Thousand Years ML is the wick to light the magical lamp