In January 2024, an anime adaption of two sagas of light novel series Monogatari—"Off" and "Monster" seasons—was announced, set to premiere in the same year.[1] Later, on May 1, the official website of the anime series teased the upcoming announcement by countdown with an image of the letter "Y" on a red-pink background, as well as posted the image by the official X (formerly Twitter) account for the writer Nisio Isin's anime project.[2][3] The next day, the anime series confirmed that Yoasobi would perform the theme song for Monogatari Series: Off & Monster Season, titled "Undead".[4] A snippet of the song was previewed via the trailer of the anime's first two arcs Orokamonogatari and Nademonogatari on May 3.[5]
Around two months later, on June 24, the duo additionally teased the song via their social media.[6][7] Five days later, they revealed the song's release date, to be July 1, 2024, and its cover artwork, which features Monogatari character Yotsugi Ononoki making a V sign with both hands.[8] The song was sourced from two short stories written by Nisio, Nadeko Past and Shinobu Future, published on the anime's website.[9]
