Hikaru Utada
The song is a pop/electronic song with an arrangement consisting of piano, vocal harmonies, percussion and synths, with occasional background 8-bit sounds. The song features background vocals by four women recorded in London in August 2010, described in the documentary "Hikaru Utada: Ima no Watashi", as Celtic. Utada chose this singing style for its nostalgic, dream-like qualities. This is the first instance of background vocals in a Hikaru Utada song not being performed by her.