"Journey (Kimi to Futari de)" is Kay's first release since Flash in June 2010, and her first single in 15 months. It was released just two weeks before Kay's ninth studio album Spin the Music. The release was first announced on September 30 on Kay's official website. The title track was featured in commercials for Japanese skincare range Attenir. The commercial began airing from October 6 onwards. The single features "HOLD ON" as its b-side. The song was used as the theme song to the 2009 film adaption of Dolan's Cadillac. It was first announced that Kay would sing for the film on August 16, 2008.
The music video for "Journey (Kimi to Futari de)" was directed by Amber[who?], it was revealed in early November. The video features a tearful Kay reminiscing on various times in a past relationship, such as Kay and her former lover together at a park and having dinner. The video then subsequently ends with Kay crying to herself softly.