User blog comment:BlackWizardZeref/Fairy Tail: Chapter 380 Hell's Core/@comment-76.124.155.27-20140413200702/@comment-7418318-20140414192527

Unless there are some serious mis-translations for the german version, Mashima did write in the after words of volume 13 that he only got the idea of keeping Natsu confined within the guild while he was drawing the arc, so that might very well be the case.