"Letters" is a song recorded by Japanese-American musician Hikaru Utada for their album Deep River (2002). It was released as a double A-side single with the song "Sakura Drops" on May 9, 2002.
Since they debuted as a musician in 1998, Utada had worked as the primary or sole songwriter for their music. Beginning with their second album Distance (2001), Utada began to co-arrange songs, such as "Wait & See (Risk)", "Distance" and "Kettobase!" The bonus track on Distance, "Hayatochi-Remix", was arranged entirely by Utada. In March 2002, Hikaru Utada released "Hikari", the theme song for the game Kingdom Hearts.
"Letters" was written and arranged solely by Utada. It featured six different guitarists all performing the acoustic guitar in the backing, including Char, Hisashi from Glay, and Teruzane Utada.
The song was used in commercials for NTT DoCoMo's 2002 range of FOMA cellphones. This was the third song of Utada's to be used in collaboration with DoCoMo, after "Final Distance" (2001) and "Traveling" (2002). On May 20, 2002, Utada performed the song live at Hey! Hey! Hey! Music Champ, a week after they performed the single's other A-side "Sakura Drops".
Utada performed the song during their Hikaru no 5 Budokan residency show in 2004, during the Utada United 2006 Japanese tour, and at the two date concert series Wild Life in December 2010.
In 2014, "Letters" was recorded by Ringo Sheena for Utada Hikaru no Uta, a tribute album celebrating 15 years since Utada's debut. It was released as a preceding download from the album on December 3, 2014.
Critical reception to the song was positive. Hayashi of Ongaku DB felt "Letters" was a "Latin-sounding number" with a melody that had a "high level of freedom". CDJournal reviewers described the song as having a "spicy Latin/gypsy" sound, and praised the "passionate melody", and noted how the upbeat rhythm contrasted with the lyrics, which dealt with "melancholic everyday feelings". Kanako Hanakawa of Shinko Music felt that the song had a mature mood, and that it was "sexier" than their other songs due to the guitar backing of so many older male guitarists. Akiyoshi Sekine of CD Data praised the song's "percussive rhythm", and praised the skill and sense that went into Utada's arrangement of the song.
Personnel details were sourced from Deep Rivers liner notes booklet.