Bang Hyun Ah appeared as the 4th mystery singer and introduced herself as Minah's sister. The debate on whether or not she's a truly talented singer and the sister of Minah heated up among the panelists. 

SEE ALSO: Ex-Rhythmic Gymnast Son Yeon Jae opens a new chapter in life and shares updates

To reveal her identity, Bang Hyun Ah performed Girl's Day's ''Something''. As soon as she sang, Bang Hyun Ah shocked everyone and proved to be a talented singer, as well as Minah's older sister. 

Minah also made a surprise appearance despite her busy schedule and showed support for her sister 

It's also turned out that Bang Hyun Ah actually made her debut in the girl group Wanna.B in 2016. 

Minah shared a comment, and said, "I wanted to be supportive but I wasn't able to provide encouraging words. I still don't know how to express it so that's why I decided to make an appearance like this. I hope my unnie succeeds. As a dongsaeng, I'll be supporting her."