這張單曲是組合在休整約一年之後發表的第一首單曲,也是組合2011年發行的第一張單曲。主打歌《Why? (Keep Your Head Down)》、關西電視台與富士電視台製作的電視劇《美麗鄰人》的主題歌[參5]。這張單曲收錄的兩首歌曲《Why? (Keep Your Head Down)》與《MAXIMUM》都是組合在韓國發行的專輯《Keep Your Head Down》收錄的歌曲(《왜 (Keep Your Head Down)》與《MAXIMUM》)的日語版本。
單曲分為「CD+DVD」「只CD」兩種版本發行,前者有收錄主打歌《Why? (Keep Your Head Down)》的MV與MV的拍攝過程(只在初回限定盤中收錄)。初回限定版本封入特典是封面大小的卡片(6種中隨機封入1種)。「只CD」版本有12頁豪華手冊同捆封入。
TRI-ANGLE(2004) · RISING SUN(2005) · "O"-正.反.合.(2006) · MIROTIC(2008) · 왜(Keep Your Head Down) / 이것만은 알고가 (Keep Your Head Down)(2011) ·CATCH ME / HUMANOIDS(2012) ·TENSE(2014) ·RISE AS GOD(2015) · New Chapter #1 : The Chance of Love(2018)
The 1st LIVE CONCERT "RISING SUN" - The 2nd ASIA TOUR CONCERT "O" - The 3rd ASIA TOUR CONCERT "MIROTIC" in SEOUL - The 4th WORLD TOUR "CATCH ME" in SEOUL
日本
TOHOSHINKI LIVE CD COLLECTION ~Heart, Mind and Soul~ - TOHOSHINKI LIVE CD COLLECTION ~Five in the Black~ - TOHOSHINKI LIVE CD COLLECTION ~T~ - TOHOSHINKI LIVE CD COLLECTION ~The Secret Code~ FINAL in TOKYO DOME
1st LIVE TOUR 2006 ~Heart, Mind and Soul~ - 2nd LIVE TOUR 2007 ~Five in the Black~ - 3rd LIVE TOUR 2008 ~T~ - 4th LIVE TOUR 2009 ~The Secret Code~ FINAL in TOKYO DOME - TOHOSHINKI VIDEO CLIP COLLECTION -THE ONE- - TOHOSHINKI LIVE TOUR 2012 ~TONE~ - TOHOSHINKI LIVE TOUR 2013 ~TIME~ - TOHOSHINKI LIVE TOUR 2013 ~TIME~ FINAL in NISSAN STADIUM - TOHOSHINKI LIVE TOUR 2014 ~TREE~