Nio Hashiri is a mysterious and playful student in the anime series 'Akuma no Riddle.' She is known for her enigmatic personality, often acting as a messenger or observer among the assassins at Myōjō Academy's 10th Black Class. Nio frequently provides critical information and manipulates situations from behind the scenes, making her true intentions hard to discern. Her role is pivotal in driving the story forward, as she influences both the assassins and their target, adding complexity to the series’ plot.