They sat in the cove, the same place they'd become friends. There was no other place to have this conversation. "I'm going back to DunBroch," he said, without preamble. Toothless, sunning himself, looked slightly bored with that revelation. "And you're my best friend, and of course I want you to go with me, but I'm not going to make you. I can't ask you to leave your home and all of your friends and family to follow me to some strange place where you'll be all alone."
He squinted slightly, chin tipped down.
"Okay, you won't be all alone; I'll be there, obviously, and Merida, and the triplets and the king and queen, but there won't be any other dragons."
He wiggled his earflaps close to his head.
"You saw their reactions. They'd obviously never seen any dragons before. Sure, there were drawings in the book, but who knows how old that was. They would have said something if there were still any dragons around."
He rolled his eyes a little, snorting.
"Yeah, I recognize the humans-don't-know-everything look by now. Okay, so maybe there are dragons somewhere around DunBroch. They could be wild—"
He opened his mouth and snapped his teeth out, a faint warning grumbling in the back of his throat.
"—By which I mean aggressive and unfriendly. I don't want to start any trouble down there."
He laughed derisively.
"All right, any more trouble than I'm bound to start anyway. I'm not so sure I want you to come anymore."
He darted his tongue out, nose wrinkled.
"It's up to you. Whatever you decide, to stay here or to come with me, you have to choose. I'm already ruining enough stuff by going; I don't want to ruin your life, too."
He butted his head against Hiccup's torso until he had to hold on or be knocked over; then Toothless closed his eyes and sighed.