Back on October 7, former X1 members Kim Woo Seok and Lee Eun Sang excited fans by sharing some suspicious photos via SNS!

In their SNS photos, the two idols posed together in matching fall-styles, also leaving the mysterious date, "201914"!

Now, both Kim Woo Seok's label TOP Media and Lee Eun Sang's label Brand New Music has confirmed the release of a collaboration single, coming this October 14 at 6 PM KST. Fans can look forward to a unique duet song between Kim Woo Seok and Lee Eun Sang, as well as a wave of nostalgia over the two stars during their former X1 days!

Did you see Kim Woo Seok and Lee Eun Sang's latest SNS updates?