"Doppelgänger" is a song by Japanese hip-hop duo Creepy Nuts from their fourth studio album Legion (2025).

The song served as the theme for the live-action film adaptation of manga series Under Ninja.

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".

[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 release.