"Solanin" (ソラニン) is a song by Japaneserock band, Asian Kung-Fu Generation. It was released as the single on March 31, 2010 and was used for the 2010 live-action film, Solanin. The music was composed by Masafumi Gotoh while the lyrics was written by Solanins manga writer, Inio Asano and described it as "a song that connects their (Taneda and Meiko) feelings". Asian Kung-Fu Generation's version of this song didn't appear in the movie, instead Rotti's version which was sung by Aoi Miyazaki.
The single's b-side, "Mustang (mix for Meiko)" is a remix of "Mustang," from their 2008 EP Mada Minu Ashita ni, which was also inspired by the manga and was used as the ending theme of the movie. "Solanin" was added as an extra track on their 6th studio album, Magic Disk and "Mustang (mix for Meiko)" features in the band's compilation album, Feedback File 2. "Solanin" and "Mustang" were ranked 1st and 7th on fans request for band's 10th anniversary live setlist on September 14, 2013.
The music video for "Solanin" was directed by Solanin's director, Takahiro Miki. The video features band members walk around the city and playing in the same gig as the movie. Masafumi Gotoh uses Fender Mustang, same guitar used by the main character.