Just hours after the release of her mini album 'Warning', Sunmi's lead single "Siren" climbed to the top of real-time charts on a total of 6 domestic music charts and achieved an all-kill.
The song topped the real-time charts of Melon, Genie, Bugs, Mnet, Naver, and Soribada.
At her comeback showcase, Sunmi stated that the song was originally meant to be for the Wonder Girls. She stated, "About two or three years ago when Wonder Girls was promoting as a band, this song was being considered as a title track alongside 'Why So Lonely'. It was determined the song wouldn't sound as great if arranged for a band, so I've been keeping it in mind and hoping there would be a time for me to showcase it." As for the song, Sunmi said, "Sirens are used as warnings, but I was also inspired by sirens of mythology. They are known as beautiful but frightening beings that lure sailors in with their beautiful voices and drag them to the bottom of the ocean... The song itself has an ambiguous meaning, so I wanted to use the word."