Novel info
Fairy Tail: Master Dragneel

The butterfly effect is the sensitive dependence on initial conditions in which a small change in one state of a deterministic nonlinear system can result in large differences in a later state.
In this case, before the S-class Trials, Natsu Dragneel decided to train in Mount Hakobe, only to missed out on said trials, one small change, but how big of an impact this change would bring?