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On February 6, 2017, Soyou and Baekhyun were announced by Starship Entertainment to be collaborating on a duet titled "Rain". The song reflects the melancholic feelings of nostalgia that accompanies the rain after a relationship comes to an end. On February 9, a teaser video of the two singers recording the song was released. On February 14, the song was released digitally accompanied by its music video. On February 15, Starship Entertainment released a behind-the-scenes video of the song's recording session.
Music video
The music video features a high school student (starred An Yu-jin, member of IVE) reminiscing on a rainy day by herself while listening to music. It hit 1 million views in less than a day from its release. On February 15, Starship Entertainment released a special clip of the music video starring Soyou.
Reception
Upon release, "Rain" quickly reached the top on every South Korean online music charts, an achievement known as "all-kill". The song debuted at number two on the South Korean Gaon Digital Chart. The song placed first on QQ Music's K-pop chart as well as on YinYueTai's weekly music video chart.
