Compared to their peers, idol band Red Velvet's ascent to stardom has been a slow burn. The five ladies, who debuted in 2014 under K-pop titan S.M. Entertainment, didn't have a genuine megahit for the first few years while rivals GFriend and TWICE became overnight sensations.

That changed in February 2017 after the success of its catchy pop funk track "Rookie" from the fourth EP album, also titled "Rookie." Last month, Red Velvet dropped another chart-topping number, "Red Flavor," which drove the group to throw its first stand-alone concert since its debut.

"When 'Red Flavor' first came out we were concerned (whether it would be a hit or not). We promoted it hard, emboldened by support of the fans. I'm happy and grateful that the song has played on streaming services for such a long period of time," member Yeri said Sunday at a press conference before the concert at Olympic Park in eastern Seoul.

The concert, titled "Red Room," was initially to run for two days from Friday but, due to strong demand for additional shows, it was extended to three days. The fairy tale-like stage production was built to recreate a room of an ordinary girl.