Before the first episode, YoonA promised to invite 3 fans to the drama set if the viewership ratings surpass 3%. This percentage was reached quickly after several episodes due to the drama's immense popularity. As a result, 3 lucky fans were invited to visit the drama set on October 12. One of the fans who got the chance to meet YoonA shared her overwhelming happiness on SNS, and wrote, "161012 Day I can never forget... The 3% viewership rating promise for 'The K2' completed keke I am so so happy that I've been selected to be one of the 3 people. I love you. Thank you."

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Ji Chang Wook and YoonA also made promises for 5% and 10% viewership ratings. For 5%, the actors will make coffee for 100 fans, and for 10%, they promised to reveal their homes. Currently, the viewership rating is at 6.6%. More lucky fans will be treated with coffees by YoonA and Ji Chang Wook soon!