Wendy and Luna have been chosen as Hidden Track No.V ‘Keyman” of February and March 2018. They will present two like-a-gem rookies to you. PERC%NT is a singer-songwriter who has a great skills at lyrics, composition, arrangement and even producing. Yoo YongMin appeared on Mnet in 2015. Yoo is a promising rookie with his sweet voice and sensitivity (Source via Naver).
Hidden Track Number V consists of ‘key man’ and ‘locker’. The point of the show is for the ‘key man’ to introduce the ‘locker’. This will be done through a course of 2 months. All 4 will put on a special live together and at the end of 8 weeks release a ‘hidden track’ single (Source and Translated from warmblue0221).
Luna (f(x)) [KeyMan]
Wendy (Red Velvet) [KeyMan]
Yoo YongMin [Locker]
 Check-In Live || VApp || at 8PM (KST)
 [Replay] Luna X Yoo YongMin & Wendy X PERC%NT Check-in LIVE || Vapp ||
Compilation Episode – without live performance || Link ||
|| Hidden Track No.V ||
|| Campaign ||
For more detail you can following the official website