"Kaibutsu" (怪物, lit. "Monster") is a song by Japanese duo Yoasobi from their second EP, The Book 2 (2021). It was released as a single through Sony Music Entertainment Japan on January 6, 2021, the same date as the duo's debut EP, The Book. As an opening theme for the second season of the anime television series Beastars, "Kaibutsu" is about a carnivore trying to coexist with herbivores in a cruel world, based on Jibun no Mune ni Jibun no Mimi o Oshi Atete, written by the anime's writer Paru Itagaki.
On November 5, 2020, it was announced that Yoasobi would perform the opening theme for the second season of the anime television series Beastars, titled "Kaibutsu". The TV-size version was previewed in the trailer released the same day.[1] The song was based on the short story Jibun no Mune ni Jibun no Mimi o Oshi Atete (自分の胸に自分の耳を押し当てて, "I Press My Own Ear to My Chest"), written by Paru Itagaki, who also wrote and illustrated the manga.[2]
"Kaibutsu" was released to digital music and streaming platforms January 6, 2021. The song was released as a double A-sideCD single, together with "Yasashii Suisei" on March 24. The single came in 2 versions: limited edition (anime edition) and fan club limited edition for members of "Club Yoasobi", Yoasobi's official fan club website. Both versions included the original songs, TV size version songs, and non-credit opening and ending video from Beastars. The fan club limited edition also included the acoustic session of "Tabun" and "Ano Yume o Nazotte".[3] Later, the song was included on their second EP The Book 2, released on December 1.[4]
Yoasobi announced to release the English version of "Kaibutsu", titled "Monster" on July 30, alongside the accompanying music video, and aired the full song for the first time on their radio show Yoasobi's All Night Nippon X on July 27. It is the duo's third English song after "Into the Night, and "RGB".[5] Later, the song was included on the duo's first English-language EP E-Side, release on November 12.[6]
"Kaibutsu" is an upbeat fast-paced song with a catchy chorus,[7] tells about a carnivore trying to coexist with herbivores in a cruel world. Although this idea is unrealistic, it still protects the herbivore. To adhere to its ideals, it decides to become strong and confront the whole world.[8] The song is in the key of A-flat minor on the verses and break, C-sharp minor on the first chorus, D-flat major on the bridge and in D minor in the final chorus, and is at 170 beats per minute with a running time of 3 minutes and 26 seconds.[9]
American magazine Time ranked "Kaibutsu" number five on its list of the 10 Best Songs of 2021, becoming the only song from a Japanese act on the list, and being described as a "seamless" integration of "a giant pophook with furious math rock riffs", "jazzychromatic runs", and "a seismic EDM-esque drop". Additionally, critics said that the song gave "yearning", and "cinematic nature" and was "wholly unsurprised" to be served as the theme song to the anime Beastars.[10]
The CD single "Kaibutsu / Yasashii Suisei" debuted and peaked at number 2 on the Oricon Singles Chart for the chart issue date of April 5, 2021, selling 23,761 copies,[16] and also number 2 on the Billboard Japan Top Single Sales chart, selling 27,275 copies for the chart issue date of March 31, 2021.[17]
The music video "Kaibutsu" was premiered on January 13, 2021, directed by Rina Mitsuzumi, with 2D animation by Kaori Onishi and motion graphics by Jun Matsuda and Cafuu.[7] The music video depicts the conflict and determination of the main character, Legoshi, that wears a sense of speed and darkness.[18] The music video surpassed 100 million views on June 22[19] and 200 million views on April 4, 2022.[20]
Yoasobi premiered the live performance "Kaibutsu" for the first time in their first online concert—Keep Out Theater on February 14, 2021, where the song was the number fifth.[21] The duo gave a television debut performance of the song at the 63rd Japan Record Awards on December 30, alongside "Yasashii Suisei", and "Moshi mo Inochi ga Egaketara".[22]
On February 4, 2021, A cover of "Kaibutsu" by Japanese singer Masayuki Suzuki was released as a promotional single from his 35th anniversary cover greatest hit album Discover Japan DX, scheduled for release on February 23.[23]
^"The Japan Gold Disc Award 2021". Japan Gold Disc Award (in Japanese). Recording Industry Association of Japan. Archived from the original on March 13, 2022. Retrieved March 13, 2022.
^"令和3年アニソン大賞". Anisong Awards (in Japanese). Retrieved November 21, 2023.