It's already confirmed that YUI will release her 21st single with the title "fight". This single will release in 5th September 2012.

Artist : YUI

Title : fight

Release Date : 2012/09/05

Tracklist : 

1. fight 
2. If you 
3. Happy Birthday to you you~YUI Acoustic Version~ 
4. fight ~Instrumental~ 

BUY! via CDJapan : w/DVD Limited Edition | Regular Edition

Source : tieba.baidu.com, www.sonymusicshop.jp
Credit : YUI Rolling News