The theme song and the musical accompaniment was provided by the rock band CreepHyp. Initially, CreepHyp was only offered to compose background music for the film, but after reading the manga, Sekaikan Ozaki asked Terada if he could write a theme song as well. Shimura also knew CreepHyp from before and liked some of their songs. In addition, the theme song Monomane written for this film is a sequel to CreepHyp's previous song Boys END Girls. In creating the musical accompaniment, Ozaki did not decide on a scene and then write a song, but rather "just picked up a guitar and wrote songs that sounded like Happy-Go-Lucky Days, and then adjusted the scale of the finished songs to fit the necessary scenes." Terada said that this was a completely different way of creating the musical accompaniment to If My Favorite Pop Idol Made It to the Budokan, I Would Die, for which he had been the music producer prior to Happy-Go-Lucky Days. References External links Anime postponed due to the COVID-19 pandemic Liden Films Ohta Publishing manga Romance anime and manga