[2] In March 2002, Hikaru Utada released "Hikari", the theme song for the game Kingdom Hearts.

It featured six different guitarists all performing the acoustic guitar in the backing, including Char, Hisashi from Glay and her own father Teruzane Utada.

Hayashi of Ongaku DB felt "Letters" was a "Latin-sounding number" with a melody that had a "high level of freedom".

[10] 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".

[13] All tracks are written by Hikaru UtadaPersonnel details were sourced from Deep River's liner notes booklet.