A mysterious dimensional rift suddenly tears open the sky above Magnolia (Fairy Tail’s guild hall) and the Grand Line (One Piece’s sea). The rift is caused by an ancient artifact called the “Nexus Orb” — a stone that merges worlds together. Neither the Magic Council nor the World Government can stop it.
When it comes to Fairy Tail and One Piece, both series have their strengths and weaknesses. Here's a comparison of the two: fairy tail vs one piece unblocked top