Human

Alex was taken aback a bit by this information. "Wait, how can that be?" he asked. "How can a beast have a human child?"

"They can if either of the parents is a human," Scarlet explained.

"I believe the first Azure Dragon was a male dragon that mated with most likely a demon of this world. It is very difficult for interspecies conception to occur, but not impossible," Bai Jingshen explained.

"But… it doesn't make sense physiologically, does it? I mean a beast and a human…" Alex hesitated to continue.

"It doesn't make sense if the beast is a beast," Bai Jingshen said. "In fact, it is pretty much impossible. However, what if the beast were not a beast?" 

"… What?" Alex asked with a confused look.

"What if the beast were a human?" Bai Jingshen asked. "You do know what a beast can do when they reach the Immortal realm, right?"