Used as the theme song for the Fuji Television medical drama Mutsū: Mieru Me, it was released as a digital single on November 18, 2015, and as a physical single on December 2 as "Kuroi Shizuku" & Coupling Songs: 'Side B', a five-song extended play packaged with a B-side compilation album as a bonus disc.

Taking a year to write, the album was partially recorded in Los Angeles, when vocalist Shiho Ochi traveled there to collaborate with Chris Cester, the former lead singer of Australian Jet.

[5] Part way through the tour, Superfly released McKee's contribution to the album, the ballad "On Your Side", as a post-album single.

She was inspired to write the song after reading the text the drama was based on, Yō Kusakabe's 2005 novel Mutsū, influenced by the mysterious atmosphere of the novel.

[13] Also featured on the single are live recordings of the songs "Beautiful" and "On Your Side" from Superfly's performance at the Tokyo International Forum in September 2015.

[13][5] The cover artwork was inspired by the title of the song, and features black liquid droplets falling from Ochi's own hair; a recording process that took over two hours to photograph.