An interesting situation arose on the May 15 episode of JTBCs Witch Hunt as a female ulzzang Lee Jae Eun appeared on the show to reveal that she had dated a male idol in the past. Kpop idols do this through parasocial interaction. But either way I highly doubt they would add you.
KakaoTalk has various methods to add friends.
You can use the User ID QR Code Contact Number and even send invite like to add a friend. This might be a slightly unorthodox request but I hope you all have a fun field day with this. KakaoTalk is the leading messenger app in South Korea. Im introvertshy kpop fan.