Hikaru's enjoying his success, bright-eyed and smiling, right up until Tamaki calls the dragon a dog. The smile drops and expression on his face rapidly changes to convey his thoughts of 'is this guy actually serious?' He forgot how stupid Tamaki could be.

"Tono... that's not a dog. It's a dragon." He deadpans helpfully, fingers twitching. How--nothing about it looks like a dog at all!