Huh? What? Oh, another human? Well, that's great and all, but as far as Toothless was concerned, Duo was sick. Or tired. Or sad. He was something. He looked down, was moving slower than normal, held himself differently. Maybe most other humans would have overlooked something like that, but for the dragon who spoke through only unintelligible noises and body language, he perfectly understood what Duo was saying through his own movements.

Whether the human was sick, tired, sad, lonely, disheartened, or whatever he was, Toothless was worried. After giving Heero a quick look over (geeze, what a scrawny thing- almost as breakable as Hiccup, no doubt) he turned his attention back to Duo, circling him with a low pitched whine before nudging his head under his hand.

Cheer up, friend!