She was in a open field doing training with her Katana, she wanted to be a great Demon Slayer like her father Yeager... Yeager was the Death Castle, the Castle Rank is a rank of slayer way above Hashira and Pillar also her mother was Shinobu the Insect Hashira... Mikume also didn't talk much, Mikume wore a Demon Slayer uniform with a black and white butterfly haori over top