A rock ballad primarily based around non-electronic instruments, the song was composed by the band's vocalist Ichiro Yamaguchi about his mental state while physically unwell and mentally frustrated, after being unable to finish writing the song "Sayonara wa Emotion".

The first of these was the band's single "Boku to Hana", released in May 2012, which was used as the theme song for the Tsuyoshi Kusanagi drama 37-sai de Isha ni Natta Boku: Kenshui Junjō Monogatari,[2] Three months later, the band followed this with the single "Yoru no Odoriko", a song that had been featured in commercials for the design school Mode Gakuen from April 2013.

[15] Soon after the band finished touring, Yamaguchi worked on a jingle for the yobikō Tōshin High School, a song that would grow to become "Sayonara wa Emotion".

[16] While he wrote "Eureka", Yamaguchi became sick both physically and mentally, developing hives and becoming disillusioned with the idea of writing music for other entities.

[16] Yamaguchi felt distressed that he could not complete "Sayonara wa Emotion" during his sickness and exhaustion, and instead developed a strong desire to release "Good-Bye" in its place.

[17] Yamaguchi asked Victor Entertainment's management to liaise with Tōshin High School, to see if they would accept "Good-Bye" in the place of the already submitted chorus of "Sayonara wa Emotion".

[17] The lyrics were directly inspired by conversations that Yamaguchi had with staff, his bandmates, and his friend and fellow musician Gen Hoshino; expressing how he felt in that moment frankly.

[17] The title was chosen by Yamaguchi to link with Japanese author Osamu Dazai's 1940s unpublished story Good-Bye.

[17] Yamaguchi's desire to release music was revitalized when he thought of an idea to stream footage of the band during their recording sessions for the song on Ustream.

They band asked Tamaki Roy to collaborate with them during these sessions because of how impressed they were in his freestyle rap skills, which they saw when he sampled Sakanaction's "Eiga" for one of his songs.

Both editions featured a remix of the song "Eiga" from Sakanaction created by electronic musician Aoki Takamasa.

[31] The band's recording session for the song featuring Tamaki Roy that was broadcast in November 2013 was included in the DVD for their single "Sayonara wa Emotion" / "Hasu no Hana", released in October 2014.

[34][35] The video was recorded in December 2013,[16] and was unveiled on YouTube on the day of the physical single's release, January 15.

[36] The video features Yamaguchi in the role of a black shawled ferryman, transporting a woman played by Ayami Nakajō across a darkened lake.

[25] CDJournal praised the song's "simple band sound" and their "primitively honed" melody and performance.

had a similar opinion, feeling that the "nostalgic" song was an expression of the band's desire to continue into uncharted musical territory.

[47] All tracks are written by Ichiro YamaguchiPersonnel details were sourced from "Good-Bye" / "Eureka"'s liner notes booklet.