| "Kaibutsu" | ||||
|---|---|---|---|---|
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| Single by Yoasobi | ||||
| from the EP The Book 2 | ||||
| Language | Japanese | |||
| English title | "Monster" | |||
| A-side | "Yasashii Suisei" | |||
| Released | January 6, 2021 | |||
| Genre | ||||
| Length | 3:26 | |||
| Label | Sony Japan | |||
| Songwriter(s) | Ayase | |||
| Producer(s) | Ayase | |||
| Yoasobi singles chronology | ||||
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| Alternative cover | ||||
 Limited double A-side single cover | ||||
| Music video | ||||
| "Kaibutsu" on YouTube "Monster" on YouTube | ||||
"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.
Commercially, "Kaibutsu" peaked at number two on the Billboard Japan Hot 100, and number 87 on the Global 200. The double A-side CD single with "Yasashii Suisei", released on March 24, debuted at number two on the Oricon Singles Chart. The song earned four wins for both download and streaming categories of Song of the Year (Japan) and Best 5 Songs at the 36th Japan Gold Disc Award, and received diamond streaming certification from Recording Industry Association of Japan (RIAJ). It was featured on Time's 10 Best Songs of 2021 list, becoming the only Japanese song on it.