He had no idea where Greg was coming from all of a sudden, but he was expecting punishment and so the way he flinched at Greg's exclamation of horror was purely instinctual and not because he was actually afraid of Greg. He went a little shut off at Greg's insistence that he was good, but he softened a little at the tone - he didn't remember what Greg was talking about, but he did recognise the melancholy there and he reached to Greg's face to try and move it away.
He clung to Greg as the healthier boy moved them, smiling at Greg's ideas and nodding, resting his head against Greg's shoulder while they moved and tracing his finger over one of those tattoos.