"PSYCHO" is a standout track from BABYMONSTER's second mini-album, [WE GO UP]. It is characterized by its bold, addictive sound, which successfully fuses hip-hop, dance, and rock genres, driven by a powerful bassline and catchy melody. The song's lyrics offer a fresh, defiant interpretation of the word "psycho," reflecting the group's unique hip-hop swagger and intensity.

Despite being a B-side track on the EP, the song's immense popularity led to the later release of a dedicated music video. The MV is noted for its cinematic, nightmare-meets-reality direction, showcasing the members' intense expressions, bold grunge styling, and powerful, perfectly synchronized choreography. The track received high praise from fans and quickly topped YouTube's worldwide trending chart after the MV's release.