This week on MBC's singing competition program 'Mask King,' new masked contestants battled it out for their chance to go up against current champion 'Klimt'!

During one of the first round battles, 'Spring Flowers' went up against 'Spring Rain,' singing IU's "Friday," her popular duet with HISTORY's Jang Yi Jung. After the performance, 'Spring Flowers' received a flurry of compliments for her clean and tight vocals; however, the panel felt that 'Spring Rain's vocal tone was a bit more rich.

After the audience voted, it was revealed that 'Spring Rain' had won the round and would advance to the next stage, meaning 'Spring Flowers' had to reveal their identity - stunning the crowd when they proved to be none other than fromis_9's Jang Gyu Ri, who had appeared on both 'Idol School' and 'Produce 48' in the past.

While she performed her reveal stage song, Lyn's "We Were in Love," panelist Nam Tae Hyun of South Club could not help but express his surprise that the identity of the masked singer ended up being a girl group idol. Both he and fellow panelist Yoon Sang agreed that they had thought she was an actress.

Meanwhile, during her reveal interview, she talked about her experiences in singing competition programs, particularly her time spent on 'Produce 48.'

"I wanted to be able to let people know more about fromis_9 through [my time on] 'Produce 48,'" she revealed when asked why she had gone on the program.

Check out Jang Gyu Ri's full reveal performance below!