The model you saw in Seung Gi’s 1 minute music video posted a photo of her and Seung Gi on location during the day they filmed.  Her name is Jung Chae Yull and she works for Esteem Models.  This photo was posted last night around 10pm KST.

https://www.instagram.com/p/31M8zcqJq1/

Credit: chaeyull_

“I filmed diligently but due to film damage, only my backside is visible😭
Still, the song is so good, I hope for it to be daebak😊
#LeeSeungGi6th#AndGoodbye“

 

Korean to English translation by Elise, Lee Seung Gi Forever