Natsu has his head down. It's not even possible to look him in the eyes anymore. Natsu takes a step closer to Zuka. 

"What are you doing?" Zuka asks. "Your willing to kill your friend to kill me?!?!"

Natsu keeps walking closer. 

"Thank you...Natsu..." I say.

As he's about to resume his attack on Zuka, someone grabs his hand. That person is Gray. Natsu looks surprised.

"Now what type of person would I be if I let you do that?" Gray smiles.

Natsu just continues to look puzzled.

"You saved me from making the biggest mistake of my life back on Galuna Island." Gray explains. "Now its my turn."