Which project group idol leader surprised audiences with an R&B cover on 'Mask King'?

A leader of a famous project group appeared on 'Mask King'.

Along with the reveal of 'Golden Pig', this week's episode also unmasked 'Nae-golas' (meaning 'nae' ('mine') + 'Legolas' from the Lord of the Rings), who turned out to be a famous boy group leader.

Last week on Round 1, 'Naegolas' battled it out against 'Jumong' and sang "It Would be Good" by Sung Si Kyung as a duet. After swiftly moving into Round 2, 'Naegolas' sang "Sofa" of Crush, a soulful R&B track about longing for your loved one. During his solo performance, audiences seem to melt from the unexpected husky voice mastering a sweet ballad track.

Unfortunately, as 'Naegolas' lost against 'Sky Lantern', the singer had no choice but to reveal himself. Right after he took off his mask, the crowd went wild as everyone saw who was underneath -- Wanna One's Yoon Ji Sung!

As a former leader of Wanna One, Yoon Ji Sung had prepared a solo stage for the very first time. He shared that he was "really nervous to be on stage alone", but that the experience was helpful indeed.

Did you guess right away that the singer was Yoon Ji Sung?