the WORLD Ruler is Nightmare's fourth full-length studio album.

Nightmare's experimentation with the styles of electronica, ambience, and usage of live brass began in this album.

[1] The tracks "The World" and "Alumina" were featured in Death Note as the first opening and ending songs, respectively.

"the WORLD" was covered by Fantôme Iris, a fictional visual kei band from multimedia franchise Argonavis from BanG Dream!

[3] The full version of the song will be featured on Argonavis Cover Collection -Mix- which will be released on November 17, 2021.