"Swallowtail Butterfly (Ai no Uta)" (あいのうた, Suwarōteiru Batafurai Ai no Uta^?, "Love Song") is a song by Chara, released under the name Yen Town Band. It was the lead single from Montage, a concept album released for the Shunji Iwai film Swallowtail Butterfly that also starred Chara. This song was used as the theme song for the film.

The single debuted at #31 on Oricon's singles charts. Two months later, after the release of the film and album, the single managed to reach #1.

The song was written by Takeshi Kobayashi, in collaboration with Chara and film director Shunji Iwai.

The music video begins with a long panning shot over a cityscape. It then shows Chara against a farm windmill. It then switches to a junkyard, where Chara and several other people are filtering through rubbish. They eventually find a working piano, which they bring back on the back of a pickup truck. Chara plays the piano as the car drives off. This scene is intersperces with scenes from the movie.

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Wikipedia