Friendships, unspeakable bonds and trusts are one of the major aspects of shounen series. This is especially true when one has been watching Naruto, One Piece and similar titles. Naruto is famous for chasing after Sasuke in the name of having strong bond with the later and Strawhat pirates trust each other with their lives.
In Fairy Tail, there’s this sense of strong, unbreakable friendship serve as a living force not only among Fairy Tail guild members but also seen in among other guild members too.