User blog comment:Bunnyllove/Have Natsu and Zeref meet before?/@comment-24155097-20131111031149/@comment-4829046-20131111044927

That's called story writing. What kind of proper story doesn't have mystery? The guessing is the fun part since we can be happy when we are right and it keeps us in suspense and also hooked since our curiosity is piqued. If a series created a mystery and revealed it in one arc itself, then we won't really feel like sticking around for the next arc since that one will have all new mysteries that we can live without if we wished.

However its different in other cases like in those detective stories. You can read most of those without really needing to go through every single story prior to it since they don't really have a direct continuation to anything and the mystery is solved in one story itself. Sure some unique characters and events may make a reappearance but you can enjoy the plot all the same without having to see a prior story.