The Korean version was released as the lead single off their fifth studio album of the same name digitally on August 2, 2011, via SM Entertainment.

Simple" became the 85th best-selling single of 2011 in Japan according to the Oricon charts[1] and is certified Gold by the RIAJ for 100,000 units shipped to Japanese music stores.

The song was written by Yoo Young-jin, which was also the writer of their previous lead singles "Twins (Knock Out)", "Don't Don", "Sorry, Sorry" and "Bonamana".

The lyric describes the reality where modern people living in a complicated world failing to achieve what they intended to and losing their love and dreams without the breadth of mind in a simple way with humorous and metaphorical words, meaning "There is no need for taking take everything very seriously.

[5] A b-side track of the single entitled "Snow White" was revealed via the group's official Japanese website on November 30, 2011.