Ally & Diaz are a Japanese hip-hop duo known for blending rap with melodic hooks and incorporating a mix of Japanese and Western influences into their sound. They emerged in Japan's urban music scene during the late 2000s and have collaborated with several notable artists, showcasing versatility across genres like hip-hop, pop, and rock.

Their most notable collaboration with ONE OK ROCK came in 2011 on the track “Let Life Be”, featuring Taka and Cypress Ueno. This collaboration combined Ally & Diaz's rhythmic rap delivery with Taka's powerful rock vocals, creating a unique cross-genre track that highlighted the flexibility of all involved artists. The song stands as a rare but memorable example of ONE OK ROCK's ventures into hip-hop collaborations during their early 2010s era.