How I became a Natsu x Erza fan.

The part that sealed the deal for me on this pairing is during the Oracion Seis Arc. Natsu wasn't taking any orders on how to deal with Jellal. He vowed to make sure Erza would not meet him and showed that even despite time passing. Natsu still held a grudge against Jellal. Gajeel hurting Lucy? Natsu was begrudgingly able to work with Gajeel to try and take down Laxus. Jellal hurting Erza? That's a no sell. Even with Brain proving a harsh match up against Natsu. Natsu would rather fight Jellal than team up with same individual to beat Brain. An indication that Erza holds a more precious place in Natsu's heart than Natsu will ever admit or allude too. What further proves this is at the end of the Arc. Natsu isn't fighting for Jellal to rescue Jellal from The Council because he wants to help Jellal. He does it exclusively for Erza. The woman being weak and Natsu seeing this forces himself to fight on her behalf.

Now, Gray is a younger brother to Erza and as everyone tries to point out. Natsu is in the same boat. Gray doesn't lift a finger nor incite the fight to try and free Jellal. It's Natsu. Gray was perfectly fine with the situation but not Natsu.

If the arguement is that they're siblings. That means Gray should have incited the rescue with Natsu. Yet, it took Natsu stepping up for everyone but Erza to jump into action.

Natsu in this moment and only this moment put aside his grudge with Jellal not because of the values and themes of Fairy Tail. He put them aside because he thought it would be better for Erza's sake.

That's what sold this ship for me.