Hyolyn, LOONA and Brave Girls are set to perform next week
The one-day event, billed as "the biggest outdoor K-pop festival in Europe ever", will take place in July
The show's mid-term rankings were also announced
Contestants were mixed into different units for a vocal showcase
The trio are now the first-ever K-pop girl group to feature on the series
Rankings for Round 2 were also unveiled at the end of the broadcast
Rankings for Round 1 were also revealed at the episode's end
Both acts revisited song from their prior groups
An introduction to contestants VIVIZ, Brave Girls, Hyolyn, WJSN, LOONA and Kep1er – plus a first look at Girls' Generation's Taeyeon as the series' host
Highlight, The Boyz and NiziU are also set to appear