The battle to challenge the reigning champion, Rose Madam, continued on the September 13 episode.
"The King of Mask Singer" is a singing competition program where contestants hide all unidentifiable markers to shine through only pure vocal talents. They wear masks to conceal their identity and to eradicate the prejudice that people often have of singers.
"Blue Flag" was the first contestant in Round 2 who sang Yang Yoseob's "Caffeine." He stepped higher against "Forbidden Love," who sang Noel's "It Was All for You."
Lee Seok Hoon shared that as a winner on the show, he knows the significance of choosing someone who promoted around the same time as he is. He also added that "Blue Flag" sings more of a contemporary style while "Forbidden Love" sings in tones when fashionable to show the voice's breadth.
Forbidden Love moved to the next round, with 18 votes gained. However, Blue Flag unmasked, revealing himself as VICTON's Han Seung Woo. He recently debuted as a solo artist. He was the brother of Secret's Han Sun Hwa, a member of VICTON, and a member of X1 formerly.
Lee Seok Hoon, who had worked with Han Seung Woo on "Produce X 101," commented that he heard the sound "H" from LOONA and Lovelyz members from the behind and then realized who it was. Also, Han Seung Woo was someone he thought a lot during the audition program period and was glad to see how he has matured since then. He believed that Hang Seung Woo has a bright future, so he cheered for him even from afar.
Han Seung Woo responded to the statement of Lee Seok Hoon that he is a teacher and a mentor to him that made him confident. He also added that even today, when he sees him, he still gets so emotional. Lee Seok Hoon provides him with strengths whenever difficulties cross. Lastly, he expressed his gratitude to Lee Seok Hoon once again.