"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.

[1] It was the lead single from Montage, a concept album released for the Shunji Iwai film Swallowtail Butterfly that also starred Chara.

Two months later, after the release of the film and album, the single managed to reach #1.

[2] 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.