Any drama where the ML has lower social/whatever status than the SML? Preferably, but not necessarily, something where the ML raises to the task rather than SML gives up the FL or FL does something.
The Story of Ming Lan - the ML and SML are both from powerful families (they both studied with the FL and a few other children of elite families under the same tutor) but the SML is a golden only child whereas the ML is the black sheep of his family and pretty much written off by everyone. The SML sort of gives up the FL (he's not brave enough to fight for her at a critical moment) but the ML definitely also rises to the occasion.
I Need Romance 3 -the SML is the FL's senior and mentor at work and the ML is a guy who she babysat when she was a kid who moved abroad and became a DJ.
Witch's Romance - I'm not 100% sure I'm recalling this correctly, but I think the SML was a doctor but also a famous photographer? Or he was a famous war correspondent / photographer? Something like that. Anyway, the FL is a journalist and the ML is several years younger than her and runs an errand boy business with his friend. He also dropped out of medical school.
Dream High - the ML and SML both attend the same performance-focused (singing, dancing, etc.) high school with the FL, but the ML is a country bumpkin.
When the Weather Is Fine- ML is an ordinary small town book store owner . SML rich chaebol type
When the Camellia Blooms- ML is a small town police officer while SML a rich famous baseball player and the baby daddy.
The story of Ming Lan- ML has bad reputation/looked down upon despite a prominent family background while SML comes from a notable family and seen as an upstanding gentleman
The Romance of Hua Rong- ML is a pirate king while SML is the prince so there is a difference in terms of status and morality
Hwarang - ML was an orphan who turned out to be royalty and became a hero. SML was a crown prince