Tough no-nonsense female in military\law enforcement, and a rich male lead that created his position\fortune himself. They fall in love against their own intentions. Have secrets from each other because of the past. Spy Wyung Wol has a bit more action, while Me Too Flower is almost purely about romance\relationships.
Both are romances about a non conventional rich guy trying to win the heart of strong willed/stubborn girl. Both male leads are reluctant about being pushed into positions of power. Both female leads are aggressive, and self-righteous. There's scheming based on jealousy, and classism, that stand in the way of both couple's happiness. There's also great chemistry in both!
Both male leads come from a similar, rough/poor, background with dreams of in a way climbing the social ladder and also painfully can't seem to let go of their first love - a relationship that is based on rather dark feelings than love. Though there is no revenge plot in "me too, flower" there is still a similar, even if minor, intense atmosphere.