Natsu had been training to take on none other than Acnologia. A random nameless dragon didn't stand a ghost of a chance really. But Natsu could see Lucy was very torn indeed. So he howed her an apologetic smile before walking up to her and giving her a peck on the cheek before whispering in her ear.

"I promise I'll be back before you know it." With that he stepped back and quickly went fire lightning mode before he disappeared with a flash turning into a streak of light and fire that was heading straight for the dragon, starting its path on the ground for now.