When Red Velvet debuted in 2014, SM planned on debuting another girl group with a darker concept, to contrast the other girls. Though the girls of this darker group were pushed aside when SM started to promote the boy rookies instead, leaving the girls in a sort of no man's land with no nothing to do but practice for their debut that they never believed would come.

It's been years since Dark Horse Entertainment has released a new group and with two successful groups on their hands, the choice of who's next is difficult. One team of girls and one team of boys battle to see who will be the next to debut, with the votes of the fans watching.