Hyorin is the voice behind the first track from the 'Black Knight' OST, "Windup Watch"!

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The music video includes romantic moments between Shin Se Kyung and Kim Rae Won's characters, Jung Hae Ra/Boon Yi and Moon Soo Ho, from the KBS drama about a man who accepts a dangerous fate to protect the woman he loves. "Windup Watch" is a playful ballad composed by SM Entertainment's Kenzie and Lee Na Il. 

Check out Hyorin's "Windup Watch" above, and let us know what you think in the comments below!