He was in Taipei for his Taiwanese fanmeeting. During the stage, he brought up a fan onto the stage through lottery. When she went to meet him, she said, "Do you remember me?", and when he couldn't, she got angry and demanded, "You said last time to meet again."
However, Lee Dong Wook did not back up and said, "You've already been on stage and you've seen me often, so do you want to go down?" The fan only laughed in surprise, and Lee Dong Wook said, "I'm sorry I don't remember you." When she apologized, he said, "It's okay. I'm sorry that I don't remember you, but I think it'd be good if you don't get angry on stage. Other fans are watching."
Hopefully she remembers his advice next time.