"Gunjō" (群青, lit. "Ultramarine") is a song by Japanese duo Yoasobi, featuring an uncredited chorus by cover group Plusonica,[1] from their debut EP, The Book (2021). It was released as a single through Sony Music Entertainment Japan on September 1, 2020. Inspired by Tsubasa Yamaguchi's manga Blue Period and based on a story text Ao o Mikata ni, the song is described as "a cheering song that inspires listeners by immersing themselves in what they like and expressing what they see."[2]
The music video was uploaded on December 1,[3] and surpassed 100 million views on May 30, 2022.[4] The English version, titled "Blue", was released on October 29, 2021.[5] "Gunjō" was certified diamond by the Recording Industry Association of Japan (RIAJ) after surpassing 500 million streams in the country, the duo's second song after "Yoru ni Kakeru".[6]
Yoasobi performed "Gunjō" for the first time as a full group, including band members, and Plusonica on the YouTube channel The First Take, uploaded on February 26, 2021.[7] After their second extended play The Book 2 announcement, Yoasobi appeared on Best Artist 2021, giving a televised debut performance of the song on November 17.[8] They performed the song at the year-end television special 72nd NHK Kōhaku Uta Gassen on December 31. The show depicted Ikura standing on the escalator downstairs to perform on the stage, where Ayase, the band members, and the orchestra gathered there.[9]
"Gunjō" was featured on Bourbon's Alfort Mini Chocolate advertisement in 2020.[10] Additionally, it was also used as a theme of Dance One Project '21, a project that supports high school's dance club held by morning show Sukkiri,[11] and accompanied the 94th High School Baseball Tournament entrance march.[12] In January 2024, "Gunjō" was mashed up with Vaundy's "Hana Uranai", and fryer chime's sound, titled "Tirori Remix 2024" for McDonald's Japan's promotional video.[13] The song appeared on the special promotional video for the live-action film adaption of Blue Period.[14]