On August 7, 2012, BoA stated in a fan meeting that she would be releasing the Japanese version of "Only One" in the winter of 2012–2013.

Official confirmation came on December 10, 2012, via Avex, that BoA would be releasing a new Japanese single.

The USB versions use two different designs, and are limited to Soul (BoA's fanbase in Japan).

The letter set included clear files (all 3 types), writing paper, and a ball-point pen.

A clear file was available to Soul members who bought one of four available formats (excluding the iTunes version).

[5] According to Oricon, the campaign commenced in November 2012 with trials in five Tokyo cafes, but only the instrumental version of the song was available prior to January 2013.

As I think people who have experienced such separation even only for once before will certainly be able to sympathize with the contents of the lyrics and the tune is really easy to remember, everybody please listen to it repeatedly.