This week, Gummy, irreplaceable singer, visits the Sketchbook. A ballad singer, who makes all the listener cry, sings a song that makes her cry. Epitone Project, the songs remembered as life's BGM music, visit the Sketchbook in four years. Babylon, the rhythm and blues singer, performs his new song for the first time. Singer-songwriter, Martin Smith visits the Sketchbook for the first time. Stay tuned to hear their amazing performances.