Boys over flowers has F4, extraordinary you has A3. Guys are fighting over the girl they want. They're both set in prestigious schools. If you liked extraordinary you you'll more than likely like boys over flowers too and vice versa.

I don't know why but for me they were kinda the same, tunnel is a bit darker but they gave me the same vibe.

I don't know why but for me they seemed similar, I think it was the "supernatural/fantasy" aspect, if you liked Abyss I'm sure you'll like W too.

When watching Mafia I get Master Key vibes, I think it's because of the way Mafia is set up it's really similar to Master Key by not knowing who is the mafia and trying to find out who they are and in Master Key they have to find out who has the Master Keys by playing games and observing the other members, but the games in Mafia arent as good as the ones in Master Key, Mafia's still an okay show though.

Both "normal" girls who marry into the morden day palace by having an arranged marriage with the crown prince (Goong) and the emperor (The Last Empress) to clear her father's debt. In Goong the FL is involed in arts and in The Last Empress the FL is involed in theatre. Goong is light and entertaining and will give you butterflies whereas The Last Empress is a bit more melodramatic, political and scheming. In both dramas you'll more than likely have second lead syndrome so be warned. If you liked one drama I'm sure you'll like the other too :).