Do As Infinity is a Japanese pop and rock band that formed in 1999 with three members: vocalist Tomiko Van, guitarist Ryo Owatari, and guitarist and composer Dai Nagao. The band's name is sometimes abbreviated as D.A.I., alluding to the fact that Do As Infinity was named after Dai Nagao. Signed to Avex Trax, the band released their debut single "Tangerine Dream" on September 29, 1999, followed by three more singles between 1999 and 2000, which appeared on their debut album Break of Dawn (2000). In December 2000, Nagao decided to devote all his time to composing the music and no longer appeared at live events. Five more studio albums were released between 2001 with New World and 2005 with Need Your Love.

With the release of their A-side singles compilation album Do the A-side (2005), Do As Infinity disbanded on September 29, 2005. The members continued work in the music industry, with Van pursuing a solo career, Owatari working with his band Missile Innovation formed in 2004, and Nagao continuing to work with other artists at Avex Trax. The band reformed on September 29, 2008, but Nagao did not return. Do As Infinity had their first new single release "∞1", in June 2009, followed by their seventh studio album Eternal Flame (2009). The band released their 11th and latest studio album Brand New Days in February 2015.