Well, if the legends saying so are true, then the True Emperor really is a descendant of the Sun Kami, Amaterasu. As I recall, Sun Spirits are also known as Salamanders, and are a form of Nature Spirit, then perhaps young Emperor Yasuhiko is actually a very powerful summoner or has the aid of a very powerful Salamander free-spirit type protecting him? After all, Salamanders do have the Guard power, and I'd say a volcanic eruption is a very potent form of the Accident spirit power.