When did Choi Joon Ki find out her real identity?

it seams in the end of episode 4 he knew it all along. what do you think?

 Rien:

He knew who she was when he first saw her in the elevator.

I don't think so. he says that when SML recognized her in the market, it was then that he made the connection.

 Rien:

He saw her family photograph before that, and saw her for the first time in the elevator If I remember correctly. So he knew how she looked.

i agree, add to that in the last episode, he mentions he also feel in love with her in the same elevator.