User blog comment:IamJakuhoRaikoben/Chapter 389: The Twin Dragons vs. The King of Hades, Review./@comment-5303512-20140620224336/@comment-108.28.233.191-20140621032658

Here's ANN's article on the subject:

http://www.animenewsnetwork.com/news/2014-06-13/back-on-may-j-to-perform-fairy-tail-anime-new-songs/.75533