You are sitting in your castle in the Hinomoto Netherworlds when an explosion occurs right next to you, knocking you off your feet. When you go to investigate...

"...Oh hey! I managed to restrain myself this time!"

It was her! The Ice Fang Princess, Ao! But why was she here attacking your castle?! She said she was going to stop!

"Hi there! I'm Fuji's daughter Ao! But everyone calls me the Ice Fang Princess! I'm looking for my dad! Do ya know where he is?! I miss him."

Ah. That explains everything. What a handful!