Tanjiro’s younger sister Nezuko used to be a normal girl but was turned into a demon after she and her family were attacked by one while Tanjiro wasn’t home. However, she resisted her demonic instincts by wearing a bamboo muzzle and using sleep to replenish her energy instead of human blood. She also has the power to grow and shrink her body, which allows her to become as small as a child and hide within a special box that Tanjiro carries her around in during the day. In short, she’s the cutest demon you’ll ever meet!