Kilia「キリア」 is Ban's younger sister.
Kilia has light blue hair and short bangs with a ponytail/braid. her eyes are light-ish red, Kilia wears a red dress with a yellowish line at the bottom of her dress with a brown scarf.
Kilia seems to be a very kind little girl and must be very close to Ban since she is always with him and because they are brother and sister.
It was said by Ban himself that Kilia used to follow Ban around all the time, everywhere, everyday but at some stage or point she passed away from starvation when she was just four years old.