“Mystery Version” was specially written as the theme song for the fifth season of the popular Japanese television drama series, Kindaichi Case Files, in which Yamada starred. In explaining the concept of the song, Yamada said, "I think the song is perfect for [the] Kindaichi [television series]. There are a lot of words and phrases that link to the story." The lyric, "In the name of the future…" is a pun for the character’s famous catch phrase, "In the name of my grandfather…". The show was broadcast on January 12, 2013, three days after the single’s release.
