He is a well-known romantic young man, and she is a talented piano girl who is obsessed with art. Two unrelated people were tied into a "quasi-unmarried couple" by family interests.
A "hidden rules" game between top men and women.
He thought she was the prey, and she regarded him as the boss to clear the level.
It wasn't until the fake act came true that he realized - the rules of this game in the name of marriage had been written by her.