The hidden content of Dong Wha Pharm’s ‘Whal Myung Su 1897 Liquid’ global campaign advertisement in which CORTIS participated is attracting attention among fans. Scanning the QR code in the video reveals additional footage, while calling the hidden phone number plays the members' voice messages. The hidden video exceeded 470,000 views in about 20 days after its release, and the number of phone calls exceeded 400,000. Dong Wha Pharm explained that it took advantage of the fact that K.O.D reads like a ‘code’ to create a participatory campaign in which fans find and share clues.