Rin Kiryuuin

Rin is a first high school student and secretly Asahi's time traveling granddaughter from the future. She returned to the past to prevent a dystopian future in which an entity known as "Charasmatic Female Pervert II" has taken over the world and reduced 90% of the male population to subservience and changing the female population into perverts. She travels back in time using a dragon shaped time machine and wields a sword which instead of cutting makes clothing more modest. Usually quiet, she is protective of Asahi, whom she treats like a grandfather, not adapting her behavior to his younger appearance.