[Rising Dragon]

Originally Posted by Komari

About Nanoha StrikerS, I though Vivio was a kid. Why is it that sometimes I see her as an adult, and there's even a figurine coming out of her as an adult? Fan-made character?

Spoiler for Vivio:

Vivio can canonically transform into her Sankt Kaiser adult mode at will, likely through transformation magic if its not something inherently special about being the Sankt Kaiser.