User blog comment:IamJakuhoRaikoben/Chapter 457: Naked Battle, Review./@comment-5894890-20151019160900/@comment-2125188-20151019182607

It's referring to the magazine called 'Magazine Special', the magazine Fairy Girls is published in. I can't speak on mangapanda's translation so I'm gonna have to check it once the raws are out, but the Magazine Special website is saying that Hiro Mashima will be drawing a 20-page omake and will feature on the cover in the next issue and doesn't say anything about a spin-off.