The EP consists of eight tracks from the duo's songs in the English language, including their previous-release singles "Into the Night", "RGB", "Monster", and "Blue".

Yoasobi released their first English-language song, titled "Into the Night" on July 2, 2021, which was translated from the duo's "Yoru ni Kakeru" by Konnie Aoki.

[11] In a Nylon interview in February 2022, Yoasobi said that they take into consideration the sound structure to choose the songs to make an English version.

[12] Yoasobi announced their first English-language EP, titled E-Side on October 29, 2021, the same day as "Blue" release, alongside its track listing, and cover artwork, scheduled for release on November 12 to digital music and streaming platforms only,[6][13] as part of "Yoasobi Nice to Meet You Countdown" to announce the duo's new information every Friday for ten weeks until their one-off concert Nice to Meet You.

[18] The full song of "Comet", and "Tracing a Dream" were played for the first time at their radio show Yoasobi's All Night Nippon X on November 10, due to asking fans via Twitter poll.