The pair got to know each other during 'Lipstick Prince', and have remained close even after the variety show ended. The interaction started with SF9 asked fans to change up the lyrics to their song "O Sole Mio". Eunkwang saw the event and responded with his version, which he sang multiple times during BTOB's behind videos.
He wrote, "Excuse me.. I made this, and it's a bit popular with our fanclub Melody. Haha. SF9 Fighting! Rowoon, I love you. 'O sole mio~ deki latte~ cafe latte~ green tea latte~"
Rowoon responded, "Wow keke. Our manager-hyung showed me this while laughing while we were having schedules in Japan kekeke. Eunkwang-hyung, thanks for participating!!! Kekekke. Eunkwang-hyung always supports us with a bright smile whenever he sees us on music shows!!! Next time, I'll see you with a green tea latte and a cafe latte."
Rowoon also tweeted a video of himself singing BTOB's "Missing You":
To which Eunkwang responded with a video of "O Sole Mio" (with special appearances from Changsub, Hyunsik, and Sungjae):
Hopefully fans can see them together more often!
로운아 맛있는거 먹으러 가자~~~— 서은광 (@BTOB_SEKwang) November 11, 2017
근데 발음이 그게 아니야