On November 26, 2024, it was announced that Creepy Nuts would perform the theme song for the live-action film adaptation of Kengo Hanazawa's manga series Under Ninja, titled "Doppelgänger".[1] The song was first previewed on the film's second trailer video.[2] "Doppelgänger" was released digitally on January 24, 2025, the same day as Under Ninja premiere in Japan, and was included on Creepy Nuts' fourth studio album Legion (2025).[3] Hiroya Brian Nakano handles the single's cover artwork and visualizer, the latter premiered on February 5, the same day as its parent album's digital release.[4][5] Daiki Kamoshita directed the song's music video, premiered on March 6.[6]
Composition and reception
"Doppelgänger" features four-to-the-floor beats and expresses various sides of doppelgänger.[7] Fans pointed out that the song had sampled R-Shitei's song "Dr. Strangelab" from his album Second Opinion, produced by DJ Matsunaga, which he later revealed that it was an accident.[8] Eriko Ishii of Real Sound commented that the song "quite lacking in color, with only a hard four-on-the-floor beat close to BPM 160 and words spit out as if chased by the high-speed beat" and "the balance between danger and humor is perfect."[9]